DROUGHT FACTS
With special application to the Ojos Negros valley,
Baja California, Mexico

V. M. Ponce and A. V. Shetty

Table 5. Conceptual model of drought intensity-duration-frequency

Climate type Superarid-
hyperarid Hyperarid-
arid Arid-
semiarid Semiarid-
subhumid Subhumid-
humid Humid-
hyperhumid Hyperhumid-
superhumid

P_ma (mm) 100 200 400 800 1600 3200 6400

P_ma / P_agt 0.125 0.25 0.5 1 2 4 8

E_ap (mm) 3000 2400 2000 1600 1200 1200 1200

E_ap / P_ma 30 12 5 2 0.75 0.375 0.1875

L_rs (mo) 1 2 3 4 6 9 12

Moderate intensity 0.25 0.5 1.0 1.5 1.0 0.5 0.25

Severe intensity 0.5 1.0 2.0 3.0 2.0 1.0 0.5

Extreme intensity 0.75 1.5 3.0 4.5 3.0 1.5 0.75

Duration (yr) 1 2 4 6 4 2 1

Recurrence interval (yr) 2 3 6 12 25 50 100

Table 6. Drought intensity-duration-frequency relations for stations near Ojos Negros valley.

No. Station Latitude Longitude Altitude
(m) No. of
years P_ma
(mm) No. of
events Average
intensity Average
duration
(yr) Average
frequency
(yr)

1 Agua Caliente 32^o 06' 54" 116^o 23' 45" 410 34 285 9 0.78 2.44 3.78

3 Belen 32^o 11' 43" 116^o 29' 08" 555 35 347 9 0.82 2.22 3.89

3 Boquilla de Santa Rosa 32^o 01' 42" 116^o 45' 16" 50 39 272 9 0.92 3.00 4.33

4 El Pinal 32^o 11' 00" 116^o 17' 30" 1350 29 517 6 0.79 3.00 4.83

5 Ensenada 31^o 53' 45" 116^o 35' 47" 50 53 263 14 0.70 2.00 3.79

6 Ojos Negros 31^o 54' 42" 116^o 15' 53" 712 46 243 13 1.23 2.00 3.54

7 Olivares Mexicanos 32^o 02' 57" 116^o 36' 51" 351 52 310 14 0.74 2.14 3.71

8 San Carlos 31^o 47' 03" 116^o 27' 00" 170
39 331 10 0.82 2.40 3.90

9 San Juan de Dios Norte 31^o 59' 30" 116^o 09' 54" 1280 27 396 6 0.84 3.00 4.50

10 Valle de San Rafael 31^o 55' 06" 116^o 14' 13" 230 21 289 6 0.61 2.17 3.33

- Average - - - 38 325 10 0.83 2.44 3.96