areas of expertise, Dr. Victor Miguel Ponce, hydrology, hydrologic engineering

 DR. VICTOR MIGUEL PONCE:  AREAS OF RECENT EXPERTISE IN HYDRAULICS, HYDROLOGY, WATER RESOURCES, AND THE ENVIRONMENT [200217]

• Stable channel design

The design of a lined channel, with a steep slope, to be hydraulically stable is governed by the well-known Vedernikov criterion. However, it can be shown that this depends on the shape of the cross section, whether trapezoidal, rectangular, or triangular. For a given section, there is a unique relationship between the exponent β of the rating curve Q - A (discharge vs flow area), and the value of V /F, in which V = Vedernikov number, and F = Froude number. In this work we use the onlinechannel15b calculator to calculate the value of β and the corresponding Vedernikov number for a rectangular, trapezoidal, or triangular cross section. Three series of tests are carried out in a hypothetical channel, keeping constant discharge Q, Manning's n, and bottom slope S, and varying the value of the side slope z: (a) 0.25; (b) 0.5, and (c) 1. It is concluded that when the bottom width b is reduced, the Vedernikov number V is reduced more quickly to values less than 1 for the lower values of z in the range 0.25 ≤ z ≤ 1.

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• Water science

2019:   The properties of water.

This article explores the properties of water, including physical, chemical, and biological properties. Most of the properties of water span more than one field, such as physics and chemistry, or chemistry and biology, or biology and physics. Understanding the nature of water requires a thorough interdisciplinary approach to science.

• Instability of open-channel flow

The theoretical foundations and relevant experience with open-channel flow instability are examined with the objective of controlling roll waves. The latter recur with relative frequency in channelized rivers where the Vedernikov number V has increased above the threshold V = 1 due to the channelization. Several examples show conclusively the existence of a definite relation between β, the exponent of the discharge-area rating, and V. As the cross-sectional shape departs from rectangular, β decreases accordingly, resulting in a drop in the value of V. A sufficient decrease in β will cause a drop in V below the threshold of flow instability V = 1.

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• Surface-water hydrology

A comparison between the conventional approach to the hydrologic balance and L'vovich's catchment wetting approach, referred herein as the cybernetic approach, reveals fundamental conceptual differences. The conventional approach is seen to be mostly suited to event hydrology, particularly for applications of flood hydrology and related urban hydrology. On the other hand, the cybernetic approach is suited to yield hydrology, i.e., for determinations of the availability of water resources on an annual basis.

• Ecohydroclimatology

In Nature, everything is related. The Earth's crust and its environment, including climate, water, soils, nutrients, flora and fauna interact with each other in time and space in endless and demonstrably self-perpetuating ways. In the meantime, humans have endeavored to explore Nature by dividing it into convenient fields. This approach has given way to several natural sciences, among them, geology, geomorphology, climatology, hydrology, and ecology. The new paradigm is the interdisciplinary approach, which strives to connect related fields into a knowledge continuum seeking to describe Nature in a more comprehensive, holistic way. Thus, the rise of the fields of ecohydrology and hydroclimatology.

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• Field ecohydrology

The presence of soil moisture gradients in otherwise similar patches of ground has been documented by measurements in the community of Tierra del Sol, in southeast San Diego County, California. These gradients may be explained by leakage from the underlying fractured rock aquifer. In all probability, leakage proceeds along planes of fracture, with a clear linear tendency. The red shank species (Adenostoma sparsifolium) has morphological and other phenological traits which strongly suggest adaptability to shallow, more or less permanent, substrate moisture. This fact explains the substantial differences between the two lone congeners: (a) red shank, which presents itself with taller specimens in the immediate vicinity of the fractures, and (b) chamise (Adenostoma fasciculatum), which is known to colonize much drier patches of ground. Thus, the rationale for the linear oasis, which owes its existence to groundwater exfiltration along linear paths. The oasis is able to sustain an arborescent shrub such as red shank, whose water affinities lie loosely in between those of the xerophytes and the mesophytes.

• Hydraulic design of open channels

The inherently stable channel is reviewed, elucidated, and calculated online. The asymptotic neutrally stable Froude number for the inherently stable channel is Fns. Theoretically, such a channel will become neutrally stable when the Froude number reaches infinity. Since the latter is a physical impossibility, this requirement effectively guarantees that the inherently stable channel will always remain well below the threshold of instability, regardless of flow discharge, thus completely eliminating the possibility of roll wave formation.

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• Online numerical hydraulics

A comprehensive review of the amplitude and phase portraits of the Muskingum-Cunge method of flood routing is accomplished. Expressions for the amplitude and phase convergence ratios R1 and R2, respectively, are developed as a function of: (a) spatial resolution L/Δx; (b) Courant number C; and (c) weighting factor X. It is concluded that the Muskingum-Cunge routing model is a good representation of the physical prototype, provided: (1) the spatial resolution is sufficiently high, (2) the Courant number is close to 1, and (3) the weighting factor is high enough, better if in the range 0.3 ≤ X ≤ 0.5. Two online calculators of the convergence ratios are developed and tested.

• Groundwater flow

The myth of groundwater resource evaluation is examined herein. Conventional groundwater resource evaluation is based on a water budget, with the following premise: There is this amount of recharge and, therefore, we can pump so much groundwater. Actually, the situation is not that simple. We reckon that groundwater is not a volume, but a flow. Under natural equilibrium conditions, recharge to a control volume is coupled with a corresponding and equal discharge from the same volume. Under developed equilibrium conditions, pumping imposes an external anthropogenic demand which draws from both recharge and discharge, increasing the former and reducing the later. Therefore, it is incorrect to base the evaluation of safe yield solely on recharge. This approach has been widely discredited over the past 20 years. The new paradigm seeks to consider both the increase in recharge and the decrease in discharge in groundwater resource evaluations. The focus has now shifted to the assessment of the effect of reduced discharge on the rest of the hydrologic system, the related ecosystem, and on society at-large. The issue is seen to reach beyond the realm of hydrogeology, to encompass the hydrological, ecohydrological, socioeconomic, institutional and legal aspects of groundwater utilization. This approach is bound to give a fresh new meaning to the concept of sustainability.

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• Surface-water hydrology

The concept of initial abstraction in the NRCS runoff curve number method is revisited, in light of the demonstrably different results shown by current models used in practice (SWMM and HEC-HMS). The runoff curve number method is lumped in time, but it has been used by way of practice as a temporally distributed model, beyond the scope of its original development. This has led to various ways of accounting for the initial abstraction. There is an urgent need to revise the concept and to develop a new standard, so that the various models will lead to similar or at least comparably similar results.

• Sustainability of groundwater

The planned industrial-scale development of solar energy in Boulevard and surrounding communities is likely to permanently change the essentially rural character of these East San Diego County communities. While the negative impacts of energy development will be felt locally, its benefits will accrue somewhere else, very likely in distant urban settings. Boulevard has an arid climate, with limited precipitation, an avowed scarcity of surface water, and often highly destructive floodwaters. Over the years, the lack of reliable surface water has forced local people to rely on groundwater for their survival.

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• Flood hydrology

Clark's original unit hydrograph and Ponce's somewhat improved version are explained and compared. Clark's procedure routes, through a linear reservoir, a discrete unit-runoff hyetograph, while Ponce's procedure routes a continuous unit hydrograph. Since the unit hydrograph has a longer time base than the unit-runoff hyetograph, Ponce's procedure provides a somewhat smaller peak discharge and a longer time lag than Clark's. The difference, however, does not appear to be substantial.

• Sustainability of groundwater

Boulevard and its surrounding communities are being threatened by large-scale energy projects that promise to permanently change their essentially rural character. The projects are wind and solar energy projects, the need for which is ostensibly being based on the State's mandate for conversion to renewable sources of energy.

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• Sustainability of groundwater

The proposed project involves the construction, installation and operation of 54 to 85 wind turbines to generate electricity, with the actual number to depend on the alternative selected. The use of water in the region is likely to change substantially when industrial-scale projects start to share the already scarce resource.

• Sustainability of groundwater

The groundwater resources of Thompson Creek, in Poway, California, are limited and not readily replenishable. Existing hand-dug wells indicate that the water table was higher, i.e., much closer to the surface, prior to the extensive groundwater development of the past 15 to 20 years. Aquifer depletion amounts to as much as 280 feet in certain areas.

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• Environmental impact assessment

The siting of the proposed Campo landfill: (a) on top of a fractured rock aquifer of uncertain characterization, (b) on the headwaters of Lower Campo Creek, (c) within close reach of the groundwater, and (d) in a region subject to strong earthquakes, poses a high risk of contamination of groundwater, of difficult and costly mitigation.

• Environmental impact analysis

The Leopold matrix and Battelle Environmental Evaluation System methodologies are used to develop the EIA for two proposed dams (La Calzada and Calicantro) in the La Leche river valley.

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• Flood hydrology

The methods of cascade of linear reservoirs and unit hydrograph convolution are shown to be one and the same when the cascade parameters are used to calculate the unit hydrograph of the convolution.

• Flood hydrology

The flood hydrology of the La Leche river flood control project is evaluated using mathematical modeling. The RAINFLO model is used to calculate flood hydrographs for the design of principal spillway, emergency spillway, and freeboard.

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• Water quality

2008:   Online DO sag analysis.

Minimum dissolved oxygen concentration and its location along a given stream, in response to an input effluent biochemical oxygen demand and a ratio of effluent discharge to stream discharge.

• Sustainability of agriculture

Assessment of impacts of irrigation development on the surrounding environment. Increased salinity and slope instability are documented.

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• River mechanics

A dimensionless formulation of the Lane relation of fluvial hydraulics. The new criteria enables improved assessment of aggradation and degradation.

• Sediment transport

Online calculation of Modified Einstein Procedure (1955). This online script will accept sediment data input and calculate total sediment load, including measured and unmeasured load, and bed material and wash load.

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• Groundwater hydrology

Assessment of groundwater potential from a hydrologic perspective. Criteria is developed to determine sustainable yield as a fraction of mean annual recharge.

• Ecohydrology /Groundwater hydraulics

Assessment of the impact of a proposed landfill on the hydrology of a small semiarid watershed.