I attended Colorado State University from September 1968
to April 1970, at the height of the student unrest.
One day I went to the Lory Student Center to a political gathering of
international graduate students. My interest was to see just what was going on.
I got there early and sat in the back of the room.
As I was beginning to relax, a student from a newly independent African country suddenly approached me in
a direct and unfriendly manner, and said: "Where are you from?"
I said: "I am from Peru."
He said: "Oh, we are friends... you are too far."
It was then that I began to realize that politics and geography can make strange bedfellows.
In December 1993, I took a UNDP consulting assignment at the Indian National Institute of Hydrology Ganges Plains Regional Centre,
in Patna, India.
On the first night at the Guest House at the Water and Land Management Institute (WALMI) Complex,
I found myself unable to eat the potatoes with chili because
the dish was too hot for my taste. So, I told the waiter to instruct
the cook to cut down the amount of chili for the next day's meal.
The next day, finding the food equally hot, I repeated the admonition to the waiter.
On the third day, when the situation didn't change, I decided to take matters into my own hands. I entered the kitchen
to explain to the cook that I was going to starve if he insisted on adding too much chili to the potato curry.
Great was my suprise to find the cook preparing the dish, not in a pot as I had expected, but directly on the floor,
as is apparently the tradition in Patna. He had piled a mountain of chili and other seasonings
and was adding a few potatoes in the middle.
I knew then why he could not comply with my order; I should have
instructed him to add more potatoes rather than to reduce the amount of chili. Thus, the moral of the story: Different cultures lead to
different perspectives.
The difference between hydrology and hydraulics continues to confuse laypersons.
Even engineers are often fuzzy about the subject.
Several years ago, at a conference in San Francisco, I met a colleague who was employed with a leading engineering firm.
He had gotten his doctorate in hydraulic engineering at a reputable school, and had eventually risen to become section head at his firm.
Yet, the title in his business card read: "Chief Hydrologic Engineer."
Knowing that he was a good hydraulics man, I could not help but to ask him how much he knew about hydrology.
He responded, smiling: "Not much, but it sells better than hydraulics."
In the 1990s, I attended a conference convened to examine the
environmental impact of the Parana-Paraguay waterway on the
Pantanal of Mato Grosso.
The day before the conference, I had dinner with an engineering colleague.
Among other topics, we discussed the subject of free-surface instability,
and I came away from the meeting greatly impressed by his grasp of the subject.
Later, we traveled to the city where the conference was to take place.
The presentation given by my colleague was highly technical
and was delivered in a monotonous voice.
When my turn came, I summarized
the findings of my work
on the hydrologic and environmental impact of the Parana-Paraguay waterway.
The last talk of the day was by a person who spoke in a very clear and engaging style, leaving no doubt that his was the best
presentation. Pleasantly surprised, and seeing that his style was quite different from what I had observed earlier,
I was curious to find out what he had majored in college.
He said: "Communications."
That explained it, but I could not help but wonder whether we had again been caught
in the age-old predicament between form and substance.
Global warming is one of the most important issues of our time.
Several years ago, I wrote a piece on global warming and submitted it
to the Opinion section of the San Diego Union-Tribune.
The article was rejected and returned to me unpublished.
Disappointed but not undaunted, I sought the advice of a friend,
who recommended that I submit the article to the Science section of the paper instead.
Here again, the article ran into trouble: It was too
straightforward, too simple, to constitute a veritable scientific piece.
By now, the issue of global warming has made it to the mainstream of public discourse.
Yet, sorting through the myriad facts and opinions remains a challenge for many people.
Nevertheless, the world continues to warm up.1
In the early 1990s, I went to
Patna, in Bihar, India,
on a consulting assignment at NIH's Ganga Plains Regional Center.
The assignment included a visit to the Kosi project, in Eastern Bihar and neighboring Chatra, Nepal.
I was accompanied by three staff engineers from the center.
The trip to the Kosi river valley took our party to the town of Birpur,
where we settled down for lunch at a place conspicuously labeled "Hotel DeLuxe".
To my surprise, I noticed that there were no eating utensils, so I made a point of requesting them.
In the meantime, my companions proceeded to eat without the utensils.
Ten minutes later, I again requested the utensils. The person in charge told me very politely that he had sent somebody to look for them.
It took another ten minutes for them to produce the utensils; apparently, they had looked for them all over town.
I later realized that there are four ways of eating in this world: (1) using
a knife and fork, as in most of
the Western world, (2) with chopsticks, as in China and other Asian countries;
(3) with a tortilla or flatbread, as in some parts of Mexico, the Arab world, and Africa, (4) with the fingers, as in many parts of India.
Kinematic waves are simplified models of unsteady free-surface flow.
Dynamic waves solve the complete equations of continuity and motion, i.e., the St. Venant equations.
Based on this fact alone, it would seem that dynamic waves must be altogether better than kinematic waves,
yet, experience indicates otherwise.
In their classical paper on the theory of kinematic waves, Lighthill and Whitham
concluded the following: "Under the conditions appropriate for flood waves... the dynamic waves rapidly become negligible, and it is the
kinematic waves, following at a slower speed, which assume the dominant role."
Woolhiser, the developer of the kinematic flow number, recalls how
he and Liggett started their joint research at Cornell University in 1964,
with the intent of showing that the St. Venant equations without simplification were
required for the overland flow problem. Yet, to their surprise, they came to quite different conclusions.1
Theory tells us kinematic waves do not attenuate.
We reckon that many flood waves either do not attenuate, or attenuate very little.
Therefore, it follows that most flood waves must be kinematic, or, at the very least, diffusion,
and not necessarily dynamic.
In January of 1992, I spent three weeks in Belgaum, Karnataka, India,
on a UNDP assignment with the Hard Rock Regional Centre of India's
National Institute of Hydrology.
That spring, back in the United States, I shared my observations with my undergraduate hydrology students.
I told them that I had not seen many fat people in India, certainly not in Belgaum.
The last day of the semester, I decided to do a review of the class in an unconventional way:
I would have
every student tell me in a nutshell what he/she had learned.
The students sitting in the front rows, usually the better students,
had a favorite topic that they particularly remembered,
such as the runoff curve number, the unit hydrograph, or the kinematic wave.
As I reached the students sitting in the back of the classroom, one of them said:
"I learned that there are no fat people in India." That was certainly not hydrology, but it
was a lesson nevertheless.
In the middle 1980s, I was advisor to the ASCE Student Chapter at San Diego State University.
The group met weekly and we invited an engineer from the local community to share his/her experiences
with our students.
For one of the talks, a well known hydraulic engineer came and spoke to us about a project that he had been involved with.
Sometime during the course of the presentation, he said that he had done routing with HEC-2. Being an unsteady flow expert,
I know that you cannot route with HEC-2. So, I felt a little uncomfortable having to correct our guest on a matter of concept.
In 1998, HEC-2 was replaced by HEC-RAS, which remained a steady flow model through its versions 1 and 2.
However, version 3, released in 2002, has the capability to perform
unsteady flow computations. Thus, now we can properly say that we can "route with HEC-RAS,"
while a similar statement was not correct in regard to HEC-2.
In July of 1997, I attended
a horse clinic at Rancho Chahuchu, in Solvang,
California.
I had a personal invitation from the trainer, and was eager to learn more about horses.
The clinic was an all-day event featuring demonstrations on how to deal with problem horses.
The attendance was low, about 20 people. As we settled down to our seats, I was surprised to find,
among the attendees, a famous Hollywood star who had a keen interest in horses.
She was accompanied by a friend, a distinguished lady who was visiting from Europe.
I was dressed properly for the occasion, with jeans, a western-style shirt, boots, a belt, and a cowboy hat which I had purchased recently,
and we sat down to enjoy the experience.
I did not strike up a conversation with the movie star, but, given the low attendance, everybody's presence was apparent to
everyone else. We moved around, trying not to miss any details. At times, I tried out my cowboy stroll,
where you walk bowing your legs to show that you are a well seasoned horseman.
Toward the end of the day, our movie star broke the ice and approached me, pointedly, and said: "You are a true Mexican cowboy."
I smiled at the compliment,
but could not help to think that she had missed it on all three counts: I was neither true, nor Mexican, nor a cowboy.
Of all my experiences as a graduate student at Colorado State University in the early 1970s,
the following is most certainly a pearl.
The class CE602 Transport Phenomena
was required for all majors in the graduate program in hydraulics.
One day, the professor came to class and, after the customary salutation,
solemnly declared:
"I have decided to do something different this time. The midterm will be take-home..." and he paused,
to continue with a grin:
"three-hour, closed book."
We looked at each other in amazement, while struggling to regain our composture. Specific instructions followed almost immediately: "You will pick
up the exam tomorrow at 5 pm in my office, and return the completed exam by 8 am the following morning."
I can't vouch for the rest of my classmates, some ten in all. All I can say is that I knew that something was up, but I could not figure out
what it was.
As instructed, I picked up the exam, went home, had dinner, and started to work on it at about 8 pm. There were six problems, the likes of which
I had never seen before. I knew almost immediately that this was not a three-hour exam, certainly not for me.
At around 2:00 am, I finally completed the work, after having consulted at least two books. At 8:00 am,
I returned the exam, half ashamed, but undaunted.
The next time the class met, the professor inquired: "How did it go?" My recollection of the events of that day is that
everybody kept quiet, except for my colleague Fred Theurer, who said, pointedly:
"Professor, I must tell you that it was impossible for me to do the exam in the allotted time,
and without consulting any books. It took me nearly six hours, and I used several books."
I am certain that Fred got an A in the exam, while the rest of the group, including myself, had to
settle for an also-ran B. We will never know if his honesty paid him handsomely that day, but I would not hesitate to place my bet on it.
Computer programming remains a challenge for many people. In the past several years,
this has led to the popularity of software applications with graphical user interfaces (GUI),
which circumvent the need to program. Yet programming remains an indispensable tool in research and other specialized
applications.
In many instances, debugging a computer program requires uncommon analytical ability and a dose of patience.
However, a debugging trick that never fails is to
print intermediate steps until the source of the trouble is identified.
In the early 1980's, a student came to me with a partially completed programming assignment, and said,
"Prof. Ponce, I have been looking at this program for more than two hours and cannot find the bug. Can you help me?"
I promptly replied, "You can't just look at the code. You need to do something about it."
And then, I proceeded to show the student a trick that I had learned very early during my graduate school days at Colorado State
University.
"Place the message 'So far so good!' as a marker in several critical parts of your code,
and pretty soon you will find where the problem is".
The student followed my advice and in very short order the assignment was completed.
In one of my trips to Oaxaca, Mexico, in the early 2000's, an acquaintance told me the following story.
A group of people from a remote hamlet were planning to build a road. A delegation converged on the mayor of town to solicit his help.
The mayor offered them a bulldozer and a few picks and shovels.
He also mentioned that he would send an engineer. At that point, the head of the delegation said:
"An engineer? What for? We haven't used one before."
The mayor explained that the engineer would help them to find where to put the road.
The head of the delegation answered promptly: "In the past, when we needed to build a road,
we just let a burro loose, and he would show us the best possible route."
Thus, the moral of the story: A burro's natural instinct
can work engineering wonders.
In July 2005, I attended the 20th anniversary celebration of the Feather River Coordinated Resource Management Group (FRCRMG),
in Quincy, Plumas County, California. The three-day event included a tour of Red Clover Creek, which for many years
has been at the center of this agency's efforts to manage river ecosystems in the California Sierras.
The story of Red Clover Creek teaches us some important lessons.
Prior to the middle 1950s, Red Clover Creek was a relatively shallow stream with permanent baseflow supporting
an excellent fishery. However, in the late 1940s and early 1950s, federal programs were introduced to eliminate willows
[phreatophytes] using aerial herbicide spraying. At about the same time, over three hundred beaver were removed from the system.
These actions, together with the longstanding effects of heavy grazing and a system of abandoned logging railroad grades in the valley,
brought Red Clover Creek to the brink of disaster.
The 1955 flood was the catalyst for the massive gully formation through the valley, which continued through most of the 1980s.
Once the gully formed, the regional water table dropped, baseflow was all but lost, and erosion and sediment transport followed. Of all the
reasons for the formation of the FRCRMG in 1985, none was more important than the loss of Red Clover Creek.
Happily, after many years of enlightened management, Red Clover Creek is now returning to its former
state: stable, self-sustaining, and with permanent baseflow.1 The restoration work began in 1985 with the installation of four loose-rock checkdams.
Ten years later, the FRCRMG developed a new technology to use in place of checkdams.
Called "pond and plug," it seeks to eliminate the gully through onsite excavation and fill, forcing the water
level in the valley to rise to meet the historic remnant channels and floodplain. In 2006 this technique was used on
additional portions of Red Clover Creek below the original check-dam project. After treatment of 4.5 miles of stream channel, the project
is now in its first season of recovery, as shown in the [before and after] photos below.2
Reading about the Spanish Conquest of Mesoamerica in the early XVI Century is a fascinating experience.
One of the most remarkable stories is that of Fray Bartolomé de Las Casas, who almost singlehandedly
engineered the institutional defense of the Indians as human beings and subjects of the Spanish Crown.
De Las Casas was witty and extremely eloquent.
He argued convincingly for many years in favor of better treatment for the Indians.
In one such meeting, in October of 1519,
where King Charles I of Spain (Charles V of the Holy Roman Empire) was to hear the arguments on what to do with the
Indians, Bishop Juan de Quevedo, who had just returned from five years in the Darién [in what is now Panama], quoted the Philosopher Aristotle as saying that "the Indians
are slaves by nature." Never short of a response, de Las Casas countered that since Aristotle was a nonbeliever,
he was presumably burning in Hell, so his argument held no ground.1
Such were the events that shaped the history of Latin America.
In 2002, I published a paper on the subject of drought
characterization in the Ojos Negros valley, in Baja California.
Mr. A. V. Shetty, one of my coauthors, had performed a detailed statistical analysis on the data for ten (10) climatological
stations in the vicinity of the valley, located 25 miles east of Ensenada.
The results showed that the average
frequency of droughts in the region was
3.96, i.e., that droughts recurred in the valley approximately every four years.
Afterwards, we followed up with a visit to the valley, where we met the owner of the Ojos Negros Ranch.
I struck a conversation with him and asked him what was the frequency of droughts
in the valley. Without winking an eye, he said: "Every four years."
Many urban people believe that the world ends at the outskirts of town. Yet, in my own experience, this is not so.
Many years ago, I traveled to Lima, Peru, where I grew up in the 1950s and '60s.
While there, I visited my father, who is from Huarochiri, one of ten provinces in the department of Lima. [The latter is
one of twenty-four departments in Peru].
As was my father's custom, he invited me for an outing.
After a little more than three hours, we reached the town of Antioquia, about 80 km east of Lima.
The place, however, is largely unknown, because a lack of a paved road discourages most people from reaching it.
That evening I met some friends at a party. One of them asked me: How are you doing?"
I said: Fine, I just came back from Antioquia." To which he solemnly responded: "There is no Antioquia here!"
In 1993, I visited for the first time the Colca Canyon, tucked away in the Andes Mountains, a few hours drive from Arequipa, Peru.
I was accompanied by a local colleague and a driver. To add a measure of interest to the trip, we decided
not to backtrack from "El Mirador del Condor" (The Viewpoint of the Condor) to Arequipa,
but rather to keep driving forward to meet the Panamerican Highway,
essentially, making what amounted to an 18-hour circuit over little-traveled gravel roads.
Along the way, we were regaled with magnificient scenery and the familiar rural landscapes of the Peruvian Andes.
Many people assume business as usual as they venture into these areas, without realizing that there are deep cultural differences.
Upon reaching the town of Huambo, I had an urge to go to the bathroom, so I instructed our driver to stop
at a suitable place. He stopped at a corner store, I jumped out
of the car, entered the store, and said to the salesperson, almost pleading: "May I use your bathroom?"
She looked at me, half surprised, half nonchalant, and said: "We do not have that here."
When I politely insisted on an explanation, she motioned to the outside, and said in a slow tone, so that she was sure that I got the message:
"When people want to go, they manage somehow."
It was a lesson in rural Peru that I would never forget.
In 1993, I spent three weeks in Bihar, India, on a consulting assignment
with the National Institute of Hydrology. I was stationed in Patna, with an occasional trip to the countryside.
The local weather is humid subtropical, with mean annual precipitation of 1,200 mm, and
significant amounts of precipitation occurring in all seasons.
At night, I would huddle under the mosquito netting and feel confident that I was protected
against the many bugs, some of which appeared to be very mean.
However,
once I turned the lights off, after a few moments, a shrieking and persistent sound would start somewhere in the room,
as if many insects were busy eating away at something. When I would turn the lights on to inspect the surroundings,
the mysterious sound would stop. This went on a number of times, until I would invariably tire out and fall sleep.
I never figured out exactly who or what was responsible for the sound, but I am certain that I was not alone during those nights
in Bihar.
In the Fall of 1993, I took a sabbatical leave
at the famed Departamento Nacional de Obras Contra Secas (DNOCS) [National Department of Works Against Droughts], in Fortaleza,
Brazil.
This work led to several papers on drought hydrology, among them,
Characterization of drought across climatic spectrum
and
Management of droughts and floods in the semiarid Brazilian Northeast - The case for conservation.
While in Fortaleza one evening, I went out to dinner with a former classmate from Colorado State University
who happened to be in town for business. He had a very good reputation in
stochastic hydrology going back to his years as a Ph.D. student.
Curious to find out what he was up to, I said: "José, what are you doing these days?"
He answered: "Urban hydrology."
I said: "That is something new to you, isn't it?
He replied: "It is simple. All you do is build a channel in the middle of the street, and drain the water
as fast as you can."
I said: "That's the way it used to be. Nowadays it is a lot more complex than that. Urban hydrology is not just drainage;
it is also retention."
In the Fall of 1997, I visited Disneyland, accompanied by two scientists from
the National Institute of Hydrology in Roorkee, India. The scientists were spending a semester at SDSU on study leave,
and I was showing them the Southern California attractions.
After enjoying several rides, we decided to get something to eat before continuing our visit. We found a burger
place nearby, and proceeded to order some food. I ordered a hamburger;
my companions, after much hesitation and consultation among themselves,
ordered cheeseburgers.
When the food arrived, my companions were surprised to learn that a cheeseburger wasn't just cheese and bread,
it had meat! They were vegetarians.
We had to quickly chart an alternate plan so that our visitors would not go hungry that day.
In the Spring of 1989, I visited Alkali Creek, in western Colorado, accompanied by a colleague, a biologist who worked
for a federal agency. My objective was to observe the watershed restoration project that had been accomplished in the 1960s
by the Forest Service. Eventually, I published a paper entitled:
"Management of baseflow augmentation: A review," in which I documented this and other
similar projects of watershed restoration.
After we had observed several of the more than one hundred check dams that were still standing,
and having suffered the inclement weather for a couple of days,
my colleague said to me, pointedly: "Victor, as I can see, the only difference between you and me
is that you make three-thousand dollars more."
Sediment problems in hydraulic engineering are difficult to solve.
A case in point: In 1992, two sediment retention basins were built in the Aguaje de la Tuna
watershed, in Tijuana, Baja California, Mexico. The intent was to catch the sediments in the event of a flood, while
letting the water pass through. The objective was to
reduce sediment deposition in the mouth of the watershed, based on the belief that sediment was more damaging than flood waters.
On January 8, 1993, a severe and unusual flood tested the sediment retention basins, which proceeded to fill up with sediment in short order.
Apparently, the problem had been solved; however, experience indicates otherwise.
To understand what may have happened, we examine Lane's relationship,
which states that sediment discharge is proportional to water discharge.1
According to Lane, if sediment load is extracted from the flow, by any means,
and water discharge is not reduced accordingly,
the water flow becomes "hungry" and proceeds to entrain new sediment as it moves downstream. This explains the well known phenomenon of
aggradation upstream of a dam and degradation downstream of it.
In the event of January 1993, approximately 400,000 cubic meters of sediment were deposited
near the mouth of the Aguaje de la Tuna, despite the fact that the
sediment retention basins had retained all the sediment they could (20,000 cubic meters).2
Two scenarios are possible:
According to Lane's relationship, the second scenario appears more plausible.
In the Aguaje de la Tuna, the
hungry water [flowing from the sediment retention basin]
scoured a depth of about 3 m in the streambed, down to bedrock [see photo].
Thus, the utility of building sediment retention basins, without providing for concurrent water storage, is cast into question.
In the fall of 1993, I spent a sabbatical leave in Ceara, in the Brazilian Northeast, researching the subject of droughts.1, 2
At that time, the region was suffering from a crippling three-year drought. The "Canal do Trabalhador" ("The Worker's Channel") was being built expressely for the water transfer.3 At the time, the canal project was regarded as a last ditch effort to mitigate the ravages of the drought. The alignment followed roughly along the coast of the state of Ceara, a distance of about 100 km. The construction of the canal was particularly difficult due to the unstable soils and the very mild slope of the canal (about 5 cm per km), which increases the risk of sedimentation. Completed in a record period of six months, the canal started delivering the much needed water near the end of 1993. However, less than two months later, a series of heavy storms filled the Pacajus reservoir, bringing to an end the long drought and rendering the Worker's Channel essentially unnecessary. Currently, the canal is not being used for its original purpose, but rather to supply irrigation projects along its alignment. Thus, the lesson to be learned is: "Weather prediction is difficult and failure prone." 1 Ponce, V. M. 1995. Management of droughts and floods in the semiarid Brazilian Northeast: The case for conservation. Journal of Soil and Water Conservation, September-October, Vol. 50, No. 5, 422-431. 2 Ponce, V. M. 2000. Characterization of droughts across climatic spectrum. Journal of Hydrologic Engineering, Vol. 5, No. 2, April, 222-224. 3 Ponce, V. M. 2004. "The Worker's Channel." Legacy tale, May.
In March of 1974, Professor Koloseus1 arrived in class at the end of the [winter] quarter at Colorado State University,
and announced that the final exam
[in Open-channel Hydraulics] "... was going to be quite different this time." We, the students, who numbered around fifteen, were supposed to
prepare our own questions and answer them as best we could. He would judge meaning, content, and accuracy, and assign a grade accordingly.
My recollection of the events has faded a bit over the years, but I remember clearly that we all complied. We
submitted the self-prepared exam, and waited for a grade... and waited, and waited....
About a week later, Prof. Koloseus showed up, visibly exhausted, acknowledging that it had taken him quite some time to grade
the exams. After thanking everybody for their efforts, he
went on to say that the experience had been so demanding [of his time and energy], that he vowed never to do it again.
Not many people are aware that the renowned physicist Albert Einstein wrote an early
piece on the cause of meandering.1 Likewise, not many people know that his son,
the famed UC Berkeley Professor Hans A. Einstein, did not begin his career in hydraulics,
but rather, turned to it after several years as a structural engineer. We can surmise that the elder Einstein had a keen interest in
meandering and encouraged his son to pursue a career in river hydraulics. History tells us that toward the middle of the 20th century,
Prof. Einstein made his mark as one of the greatest contributors to the nascent
field of
sedimentation engineering. His 1950 sediment transport model is the forerunner to the
Modified Einstein (1955), Colby (1957) and
Colby (1964) methods.2
Einstein's discussion on the cause of meanders is casual, but characteristically insightful.
His attribution of secondary currents to the Coriolis force [produced by the Earth's rotation]
may have been among the first. His
explanation of how meanders form due to a balance between inertial and frictional forces in a direction perpendicular to the
motion is masterful.
To this date, we are still not 100% sure of the process, but one thing is certain:
Einstein's thoughts have helped us come closer to unraveling the mysteries
of river meandering.
There are three types of errors in mathematical modeling: The first two types
are widely recognized, while the third type is often overlooked.
Data of questionable quality may be due to inappropiate procedures, recording errors,
equipment defects, and/or nonstationary of the data.
Thus, mathematical models must not necessarily seek, in all cases, to match the field data.
In 1995, I completed a study entitled "Hydrologic and environmental impact of the Parana-Paraguay waterway on the Pantanal of Mato
Grosso, Brazil."
Earlier, I had traveled to Rio de Janeiro, Brazil, and met with my friend Newton Carvalho,
who had spent several years doing field measurements in the Upper Paraguay river. Together we visited the appropriate agency
in search of the field data to use in the study. There was plenty of gage data, which we collected dutifully.
In addition, we found a limited amount of hitherto unpublished sediment
data, consisting of monthly sediment concentration at two gaging stations,
Cáceres and Porto Esperança,
for a five-year period
(1977-82). Newton himself had participated in the sediment measurements. I thought it important to publish the sediment data,
not only to complement the hydrologic impact study, but also for purely historical reasons.
The study report was published in August 1995.1 Several months later, I got a call from Steve Hamilton,
from Michigan State University.
He mentioned to me that in his experience, there was something wrong with the published sediment measurements. Some of the concentration values
appeared to be too high. A bit puzzled, I called Newton, looking for clarification.
I asked him: "Newton, can you think of anything wrong with the 1977-82 sediment data for the Upper Paraguay?"
He paused for a moment and said: "As a matter of fact, now that you mention it,
we had some sample leakage during transport, which may have caused some of the concentration values to be too high."
Thus, the moral of the story: "Publication of data does not imply that is it correct."
In 1989, I purchased a popular hydraulic package from a software reseller in San Diego.
The package came with a supplement, which consisted of ten programs to solve various hydraulic problems.
I took the software to Santa Cruz de la Sierra, in Bolivia, and installed it in an IBM PC 286, which was used in
those days.
At the time, I was working on a sediment routing model for the Pirai river basin.
Great was my surprise to find one of the supplement programs all too familiar. It was a program to calculate
the Modified Einstein Procedure (now available online). The form of its output left me no doubt that it was my own software,
which I had developed at Colorado State University in the middle 1970s.
During my time at Colorado State University in the late 1970s, I had the pleasure of casual interactions with Prof. Vujica Yevjevich,1
a man of many talents. At that time, he was in charge of the Civil Engineering Department's graduate Hydrology Program, while
Prof. Daryl Simons
was head of the Hydraulics Program. Many students who graduated in these programs now lead the development of hydrology and hydraulics
around the world.
Prof. Yevjevich had a good sense of humor. Once he told a group of students that, judging by his own experience,
if you were a hydraulics person, your progeny was going to be male; conversely, if you were a hydrology person, it was going to be female.
For proof, he simply stated that he had three girls,
while Simons was the father of three boys. Following this reasoning, if you work in both fields, as many civil engineers do,
your progeny will be mixed. It did not take me too long to figure out that this was my case: I have a son and a daughter.
The Yevjevich progeny rule may not always apply; the exceptions confirm the rule. But one thing is for sure:
it is a good tale.
I wonder if it has something to do with
hunting and gathering, the proverbial genetic traits of male and female. Hydraulics may be more in tune with hunting,
while hydrology resembles gathering.
The natural function of rivers is to carry the sediments and dissolved solids to the ocean. Humans interfere with this function as they
utilize the water resources of the Earth, often without realizing that the water is already committed by
Nature as a carrier of sediments to their ultimate destination.
To help us understand this process, we examine Lane's principle of fluvial hydraulics: 1
in which Qs = sediment discharge, d = particle diameter [sediment size], Qw = water discharge, and S = slope of the stream. Although qualitative, this relation is extremely useful in sedimentation engineering because it links together four of its most important variables. Since, by definition, sediment concentration is: Lane's relation could be interpreted as Cs being directly related to S and inversely related to d: where, in general, a and b remain to be determined (Ponce, 2008). According to Lane, an increase/decrease in any of these variables will trigger a corresponding change [increase or decrease] in one [or more] of the others, until [a new] equilibrium is established.
Lane's principle is applicable wherever any of the four aforementioned variables is subject to change. For instance, if we take water out of a river [through a diversion], a new equilibrium will establish itself in the downstream river reach and the diversion canal. Likewise, if we take only the sediment out [with a sediment retention basin], the "hungry water" flowing downstream of the retention will seek a new equilibrium, usually through additional erosion, either downcutting or bank caving, depending on local conditions. Thus, geomorphological adjustments are the net result of changes in water and/or sediment discharge. 1 Lane, E. W., 1955. The importance of fluvial morphology in hydraulic engineering. Proceedings, American Society of Civil Engineers, Vol. 81, Paper 745, July.
In the late 1970s, I attended an ASCE Hydraulics Division Specialty Conference in College Park, Maryland.
One of the papers presented there dealt with the numerical modeling of unsteady flow, a hot topic in those days.
During the presentation, the speaker stated that flood wave attenuation was due to channel friction.
I waited until the end and approached the speaker on a one-to-one basis. I said, "I do not think that channel friction, per se, is the
cause of wave attenuation. If this is the case, how is it that kinematic waves, which are governed by friction, do not attenuate?"
The speaker sensed I had spoken correctly, and said: "You are right. We need to take another look at this."
A few years later, seeking to clarify the issue, I wrote a technical note
on the subject.1 We now know with certainty that wave attenuation is caused by the interaction of channel friction with the pressure gradient (the diffusion wave)
or channel friction with inertia (the dynamic wave), but not by channel friction interacting with gravity
(the kinematic wave).
The choice between vector and
raster formats permeates all walks of computer-based contemporary life.
The question is: Which one is better suited for a specific application?
Vector imaging is line-oriented, scalable, and uses scant computational resources.
Raster imaging
is pixel-oriented, nonscalable, and uses a comparatively greater amount of resources.
Vector imaging requires a considerable amount of work to achieve near photo
quality. Raster imaging has a high photo quality from the start.
Vector is hard, raster is easy;
vector is light, raster is heavy;
vector is specific, raster is general; vector goes to the point, raster beats around the bush.
In certain cases, vector will be the better choice;
in other cases, raster will be superior.
A compromise may be the best strategy: Use vector when speed and effectiveness are paramount;
use raster when graphical beauty outweighs every other consideration.
Navigation on the Upper Paraguay river, between Cáceres, in Mato Grosso, and Porto Murtinho, in Mato Grosso do Sul, Brazil,
has been a concern of many (see map below).1
In the late 1960s, the United Nations Development Programme (UNDP) funded a five-year study to collect hydrologic data on the Upper Paraguay,
with the intent
to use this data in future navigation development projects.2
The project was initiated in 1968, ending in 1973, with an expenditure of about U.S. $ 5 million.
Yet the Upper Paraguay was not to be tamed. The river remained in drought
from 1962 to 1973, the longest on record (see figure below).
The untimely drought on the Upper Paraguay meant that the five-year
study was only able to collect data during low flows. Thus, the moral of the story: "When dealing with the weather, be prepared to lose."
My wife Jane and I had invited our friend Alberto Castro to dinner at an Italian restaurant in San Diego. We have enjoyed Alberto's friendship for many years. Alberto is Mexican; he was born in the state of Tabasco and now lives in Tijuana. The word "Tabasco" must have come up during the conversation, because we were surprised and amused when the waiter suddenly approached our table and said: "Here is the Tabasco sauce that you ordered."
In 1977, while I was on the faculty at Colorado State University, I had the pleasure of meeting and working
with Dr. Horst Indlekofer, who was at CSU on sabbatical
from the Technical University of Aachen, Germany. Horst and I wrote two papers on the convergence of numerical models of
water and sediment routing.1,2 The numerical properties of sand-wave models was a
particular focus of our research.
One day, Horst invited me to dinner at his home.
While I was there, I noticed that he had several excellent paintings on the walls of his apartment.
I learned then that he liked to paint as a way of relaxing after a tiring day at work.
One painting particularly interested me, because
it depicted in full color the instability of the sand waves that we were modeling at school.
A couple of weeks later, I invited Horst to dinner at my home. Horst arrived with his wife, and to my surprise,
presented me with his painting on the instability of the sand waves. He said that since I liked it, I should have it.
Of all my experiences at CSU, this is certainly one of the most memorable.
To this day, Horst's painting hangs on the wall of my house and brings back fond memories of bygone years.
1 Ponce, V. M., H. Indlekofer, and D. B. Simons. 1978.
Convergence of four-point implicit water wave models.
Journal of the Hydraulics Division, ASCE, 104(HY7), 947-958.
In the Fall of 1993, I was invited to give a lecture at the São Carlos School of Engineering, of the University of São Paulo,
in São Carlos, Brazil.
I spoke about the effect of cross-sectional shape on channel hydraulics, a topic which I had been researching at the time
with Pedro J. Porras,
one of our graduate students. Some time later, we published a paper
in the ASCE Journal of Hydraulic Engineering.1
As he introduced me to his students, my host, Dr. Fazal H. Chaudhry, mentioned that in his opinion,
we were one of the very few
to research the subject of the cross-sectional effects on the flow hydraulics. He was correct, and I was very pleased with the uncommon recognition.
Many people shun failure without realizing that it is the path to success. In the early eighties, my friend Rick Fragaszy and I had season tickets to the SDSU Aztec basketball games. As with all spectator sports, Aztecs in particular, we had to sit through many mediocre games, but every ten games or so, an excellent game made it all worth it. It did not escape my attention at that time that if we had not had season tickets, we probably would have missed the good games altogether. Thus, the moral of the story: You have to experience a lot of failures before you can enjoy one success. Failure defines success; this is the true meaning of success.
In the late 1990s, I invited a former graduate student, who was very successful in his practice,
to give a guest lecture in one of my classes.
After the lecture was over, one of the students in the audience asked him what he thought about our graduate program.
He said, in a voice loud enough so that I could not help but overhear it:
"It is great. I recommend it highly. There are three professors: Chang, Ponce, and Stratton.
Prof. Chang wrote everything on the board; you didn't want to miss anything, because it was going to be on the exam.
Prof. Ponce was teaching us for the future, so you didn't have to write anything down.
Prof. Stratton threatened to flunk us all on the first day of classes, so we were forced to study very hard.
All three professors were quite different and, as a matter of fact, complemented each other very well."
Rivers transport two types of suspended sediment: (1) bed-material load, and (2) wash load.
Bed-material load is the fraction of sediment load whose particle sizes are significantly represented in the channel bed.
Wash load is the fraction of sediment load whose particle sizes are not
significantly represented in the channel bed.
The bed-material transport rate depends on the hydraulics of the flow, while the wash load concentration
is independent, for the most part, of the hydraulics of the flow.
Under steady conditions, there is a sediment rating curve, i.e., a unique relation between
water discharge and corresponding sediment (bed material only) discharge. A calculation of sediment transport rate
calculates a point (or
points) of the rating curve.
This sediment discharge is often referred to as the "sediment transport capacity," to denote that it is the amount of sediment
that the
river will always carry under steady equilibrium conditions.
Under unsteady conditions, several scenarios are possible, and the resulting effects are noted:
The second case, in particular, merits careful consideration due to the significant practical implications.
This situation usually happens downstream of a dam impoundment. The dam ponds the water and retains most of the sediment.
The water subsequently released
is typically almost devoid of sediment; therefore, it is "hungry water." This water will have the tendency to pick up
sediment as it moves downstream.1
The "hungry water" condition is exacerbated in the case of a sediment-retention basin.
Holding on to the sediment behind the dam and releasing the water immediately, without the sediment, will produce
channel and bank
erosion downstream. Depending on the rate of water release, the amount of erosion will be commensurate with
the quantity of sediment retained at the basin. Thus,
a sediment-retention basin is generally not an effective strategy for sediment control in natural streams.
The U.S. Army Corps of Engineers HEC-RAS model (Version 4.0) can perform three functions: (1) steady flow, (2) unsteady flow, and (3) movable boundary flow.
The steady flow component uses the standard step method for the solution of steady gradually varied flow.1
The unsteady flow component uses a numerical solution of the equations governing gradually varied unsteady
flow in open channels. The movable boundary component uses the sediment continuity and one of several
sediment transport equations to calculate
river bed aggradation/degradation.
• When should unsteady flow be used?
This question is of considerable practical
interest, since unsteady flow is significantly more complex and requires more data than steady flow.
However, the answer is not straightforward, requiring some elaboration.
• Steady vs unsteady flow
Under steady flow, the user inputs as boundary conditions a discharge upstream and a stage downstream.
The model calculates stages throughout the interior points, keeping the discharge constant.
Under unsteady flow, the user inputs a discharge hydrograph at the upstream boundary and a discharge-stage rating
at the downstream boundary. The model calculates discharges and stages throughout the interior points.
Under steady flow the discharge-stage ratings are unique, i.e., kinematic. On the other hand, under unsteady flow the model itself calculates (dynamic)
looped discharge-stage
ratings according to the variabilities of the flow. Therefore, the specification of a unique discharge-stage rating at the downstream boundary
contradicts the solution at that boundary.2 The model cannot be kinematic at the downstream
boundary and dynamic everywhere else!
A way out of this difficulty is: (1) to move the downstream boundary further downstream, (2) to specify the unique discharge-stage rating at the
artificial downstream boundary, and (3) to let the model itself calculate the looped ratings at the interior points,
including the point where the real downstream boundary is located.3 Despite its
apparent artificiality, this procedure works well
and circumvents the need to know the discharge-stage rating (at the downstream boundary) before it is calculated.
• Kinematic vs dynamic waves
The decision to use unsteady flow will depend on whether the wave to be modeled is kinematic
or dynamic. If the wave is kinematic, (1) the discharge will not vary in space;
(2) the discharge-stage ratings will be unique; and (3) the downstream boundary can be specified as unique.
In this case, the solutions of steady and unsteady flow are essentially the same; therefore, the unsteady flow calculation is not needed.
On the other hand, if the wave is dynamic, (1) the discharge will vary in space, attenuating as it moves downstream;
(2) the calculated discharge-stage ratings
will not be unique; and (3) for better accuracy, the downstream boundary should be artificially moved downstream to allow for an unsteady looped rating to develop
at the real downstream boundary. In this case, the unsteady flow calculation is justified, assuming of course, that the wave is truly dynamic.
• Use of unsteady flow in channel design
This situation begs the question of whether a certain flood wave can be construed as either kinematic or dynamic.
Or, better yet, whether a dynamic wave should be used at all to determine stages in the design of channel improvement projects.
On typical projects, of limited channel lengths, a kinematic wave, which keeps its discharge constant,
is a better assumption than a dynamic wave, which attenuates its discharge. Indeed, the kinematic wave assumption assures that the
channel will contain all waves, kinematic or dynamic. Viewed in this light, the use of a dynamic wave for the calculation of stages in the
design of channel improvements projects does not appear to be warranted.
1 Chow, V. T. (1959). Open-channel hydraulics. McGraw-Hill. 2 Abbott, M. (1976). Computational hydraulics: A short pathology. Journal of Hydraulic Research, Vol. 14, No. 4. 3 Ponce, V. M. and A. Lugo. (2001). Modeling looped ratings in Muskingum-Cunge routing. ASCE Journal of Hydrologic Engineering, Vol. 6, No. 2, March/April, 119-124.
In 1996, I visited the U.S. Army Corps of Engineers' Hydrologic Engineering Center, in Davis, California.
There I met Arlen Feldman, who was at the time head of research at the famed center.
I asked Arlen what was the status of the HEC-1 model, since I had heard rumors that it was being replaced with a graphical-user-interface (GUI) version.
Arlen responded that they had placed HEC-1 on the back burner, and that they were working steadily
to release the GUI version as soon as possible,
to be renamed HEC-HMS, for "Hydrologic Modeling System." (Version 1.0 of HEC-HMS was released in 1998).
I complimented Arlen on their efforts and was about to leave when
he said: "You know, in order to acquire the GUI capability, we almost had to sell half of the shop."
Many other established hydrologic models have not made the transition to the GUI version.
I wonder if it had something to do with what Arlen was referring to.
In the summer of 1986, I spent two months in
Brasilia, Brazil, on a consulting assignment with the Organization of American States (OAS) at
PLANVASF (Development Plan for the São Francisco Valley).
The work entailed developing and running a computer model of reservoir routing, a job which had me
working around the clock with the computers of the day (a vintage mainframe Burroughs, which took
all of six hours to run my job).
The last day of my stay, I decided I had worked long and hard, and looking for some
adventure, I rented
a car and headed for the new mall at the outskirts of town, intending to buy a present for my wife.
After spending a couple of hours at the mall, it was time to return to the hotel,
but I could not remember which of the doors I had come in. They all looked alike!
My concern turned into despair
when I realized that I did not even remember the color or make of the rental car.
There I was, in a singular predicament:
The mall was an island surrounded by a sea of parking lot,
and I didn't know where the car was. I couldn't even describe it, other than to say that it was a compact,
a popular size in Brazil.
I spent at least an hour retracing my memory, and trying the key on several cars, hoping
that nobody would notice; a most enduring experience that I swore never to be caught in again!
In the early 1970s, I was employed as a civil engineer with a leading geotechnical consulting firm in Lima, Peru.
Over a period of several years, I was in charge of many soil investigation studies.
One such study
took me to the site of the Sheraton Lima Hotel, a 20-story high-rise which was being planned
at that time near the center of the city.
The geology of the region is well known, consisting of well compacted alluvial material,
mostly sand, gravel, and boulders,
an ideal material for foundations. However, the owner's engineer was not sure.
To reduce the risk,
he requested three exploratory drillings, each to a depth of 30 m,
to make sure that the soil was competent to carry the design loads.
We argued that open pits would be cheaper and safer to properly ascertain the
characteristics of the soil profile,
and, on this basis, were awarded the contract to perform the study.
We hired a team of tough, seasoned Peruvian miners from Huancavelica,
led by a man named Zenón. Our team completed the three soil pits, each 1.5 m in diameter and
30 m in depth, in about three weeks. We confirmed the existence of well compacted granular material
throughout the soil profile at all three sites.
Once the work was completed, the owner's engineer could hardly believe it!
He was particularly impressed that we had accomplished the work
without any bracing or fancy equipment, using just a pick and shovel and
an old-fashioned tripod, pulley, and bucket assembly.
He ordered the holes filled with concrete and the contract paid in full.
Thus, the moral of the story: You don't have to be fancy to be effective.
Not too many people know that Niccolò Machiavelli and Leonardo Da Vinci, the famed Florentines, collaborated on a singular civil/military
engineering enterprise to deprive the city of Pisa of
water, with the hope of subduing it. By the Spring of 1504, Pisa had been independent of Florentine rule for
nearly a decade.
At that time, Leonardo convinced the rulers of Florence,
located upstream of Pisa, to construct a canal to divert the waters of the
River Arno, thus depriving Pisans from the water that they had become accustomed to.
The scheme was difficult at best, but Leonardo had a reputation to uphold and was convinced that it could be done.
Machiavelli, who at the time was Vice-Chancellor
of the Florentine Republic, was put in charge of supervising the operation.
The diversion of the Arno was
promoted not only as a way to subdue the Pisans, but also to provide flood control to the city of Florence.1
While the canal was technically Leonardo's brainchild,
the actual task of construction, which started on August 20, 1504, was entrusted to a relatively obscure engineer named Colombino.
The builder made some changes to Leonardo's design, primarily to appease Machiavelli's urging for haste.
When things did not work according to plans, Machiavelli began to doubt the canal design.
To make matters worse, by the first week of October,
a violent storm struck, which caused the walls of the canal to collapse.
Thereafter, the project was speedily abandoned and
the Pisans came out to fill the ditch.
Thus ended Machiavelli and Leonardo's brief and ill-fated incursion into
hydraulic engineering.
In the early 1970s, I was employed as a civil engineer with a consulting firm in Lima, Peru.
My job would usually take me on field assignments throughout the country, typically for a few days at a time.
Once assignment took me to Pucallpa, a relatively large city in the heart of the Amazon rainforest.
I had planned to look for a suitable hotel, but a relative convinced me to stay at his house instead.
The house, like many others in Pucallpa, was built on stilts, literally on top of the rainforest, presumably for flood protection.
The first night after work, I settled down for a well deserved rest. Suddenly, I noticed that I was not alone in the room.
There was a big cockroach at a corner, apparently staring at me, so I decided to kill the intruder. And so I did.
As I turned off the lights, the dim clarity of the new moon came in through the open window.
A few minutes later, I again had the strange feeling of not being alone, so I turned on the lights, this time only to see
many of the despicable bugs, certainly too many to kill.
Belatedly, I realized it was their house and that I was just
a guest that night, so I decided to make peace with them.
I turned off the lights and went back to sleep.
In the mid-1970s, I was pursuing a Ph.D. at Colorado State University, and I was fortunate to be at the right time at the right place.
There, I had the honor and pleasure of close association with a select crop of students from all over the world.
One of these students was Fred Theurer, who, in 1975, completed a Ph.D. under the supervision of Dr. Everett Richardson, "Rich" to his many students.
After graduation, Fred returned to his employment with the Natural Resources Conservation Service,
the former Soil Conservation Service (SCS), in Washington, D.C. He told his bosses that the convex method was no good, and that it had to be
replaced by a better routing tool, still to be developed. Indeed, the convex method, developed by SCS
in the mid-1950s, was a linear kinematic wave model featuring built-in, uncontrolled numerical diffusion.
In practice, this meant that it lacked consistency, i.e., that a routed hydrograph
could not be reproduced by substepping the reach length.
In other words, the convex method was grid-dependent; two choices for grid size (time step and space step) would invariably
give two different answers.
Seeking a proper replacement, in the late 1970s, SCS developed the Att-Kin model, which stands for
"Attenuation-Kinematic." The Att-Kin method divided the routing into two sequential steps: the first
designed to provide reservoir attenuation, and the second to provide pure kinematic translation. While the
model fared well in tests designed to prove consistency, it was not without its pitfalls. The matter was clarified
in the 1990s, when the Muskingum-Cunge method was further developed and tested.1 It is now generally agreed that
the Muskingum-Cunge method is the only hydrologic channel routing method that is stable, convergent, and consistent
(i.e., grid independent), when used within its recommended parameter ranges. This is because the Muskingum-Cunge
method simulates not the kinematic wave model, but the diffusion wave model.2
I met Prof. Arie Ben-Zvi, of Ben-Gurion University of the Negev, in New Delhi, India, in December of 1993, while attending the
International Conference on Hydrology and Water Resources. This conference was
convened to honor Dr. Satish Chandra, at the time Director of the [Indian] National Institute of Hydrology, on occasion of his retirement.
I recognized Ben-Zvi by his nametag, and being somewhat familiar with his early work,
I engaged him in conversation.
Ben-Zvi had a pleasant demeanor.
He confirmed that in the early 1970s, he had completed a Ph.D. at the University of Illinois under the supervision of
Prof. Ven T. Chow.1 His thesis dealt with the application of the dynamic wave to overland flow
in a two-dimensional context.
He confided to me that he had not used the model since the time of his graduation.
In hindsight, we now know that the dynamic wave does not apply to overland flow, because the prevailing slope is usually
large enough to make the flow either kinematic or diffusive. For the dynamic wave to be applicable, the prevailing slope
would have to be very small, say, on the order of 0.0001, which is typically not the case.
Many similar experiences confirm this conclusion. For instance, Woolhiser mentions that in the 1960s, he and Liggett
set out to prove the applicability of the dynamic wave to overland flow, and, after much study,
ended up changing their minds.2,3
Instead, they focused on the applicability of the kinematic wave,
which led to the development of the kinematic flow number.
1 Chow, V. T., and A. Ben-Zvi, 1973. The Illinois Hydrodynamic Watershed Model III (IHW Model II). University of Illinois at Urbana-Champaign,
Civil Engineering Studies, Hydraulic Engineering Series No. 26, 47 p.
During my visits to India in the early 1990s, I had the pleasure of being
invited to dinner on more than one occasion.
Invariably, the experience was delightful, although the social customs were quite different.
Dinner was usually served much later than the time of the invitation.
When appropriate, a strategically located curtain opened up to a view of a dining table filled with a great variety of dishes.
Later, I learned that it is a local custom to start preparing dinner only when the guests arrive, in order to
assure freshness. All the while, the extra time before dinner encourages conversation.
The great number of dishes showcases the diversity of Indian cuisine, while guaranteeing that the guests will not go hungry.
In January 2010, we produced a webvideo featuring Japani, an ancient Peruvian community whose remains date
back to the XVIth century. Japani is tucked away high in the mountains of the Santa Eulalia valley, near the present-day town of Carampoma,
about 100 km northeast of Lima.1
On the return leg of the trip,
we stopped at a local kiosk for well deserved refreshments.
The vendor, a hardened old lady who appeared to be in her 80s,
inquired where we were coming from.
I said: "We just came from Japani."
She promptly proclaimed: "There is no Japani here."
She went on to say that she had lived in the valley all her life, and that she was pretty sure there was no place called Japani.
In the Winter of 1976, I spent three months in Pakistan
performing the field work which was part of my doctoral dissertation.
At that time, I was employed with the Alluvial Channel Observation Project (ACOP) and led a
hydrographic surveying team.
We were researching the meandering thalwegs that were developing on the Link Canals
of the Indus Basin Irrigation System.1
Our assignment at the time was the Q-B Link (Qadirabad-Balloki), near Chuharkana, Punjab.
One day our field crew decided to start early, and had to miss breakfast at the Guest House. We had planned to pick up something to eat along the way.
We stopped at a very small and unassuming eatery, and I ordered two fried eggs and a glass of milk.
To my pleasant surprise, the eggs tasted among the best ever.
I was curious to find out where they got their eggs,
so I inquired with the attendant. He went in the backroom, and seconds later produced the hen
that had laid the eggs. Those were fresh eggs, no doubt.
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