The Ecology of Tijuana Estuary, California: An Estuarine Profile

also limitrng Hot, dry desert winds can be
devastatrng, especraily when they co~nc~de with low
t~de. it is a cltmate wtth many extremes; some
years and decades have little rarnfall and runoff,
other years have winter storms that cause
tremendous floods However, precrpltation data
ind~cate that storms are always of brief durat~on
Data for srx stations wlthin the Tijuana Estuary
watershed (F~gure 7) show the seasonal patterns of
ratnfall and evaporat~on At all stations,
evaporat~on exceeds precip~tat~on in nearly every
month The more Inland staf~ons have lower ratios
of evaporation and precipitaiion, as is typical of the
western sides of mountain ranges (Table 1).
Annual rainfall averages are about 25 cm (10
inches), most of which falls between November and
April. Although some winter months have heavy
rainfall, monthly averages are less than 5 cm (2
inches). Annual evaporation rates are very high.
Averages at Chula Vista for 1919-1981 (IBWC
1981 ) are 161 cm (64 inches) per year, with the
maximum occurring in July (1 9 cm - 7.6 inches
per month). Even in winter, substantial water
losses can occur. The minimum monthly average
evaporation is for December, with 7 cm (2.8
inches).