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Records of precipitation, water levels, and estimates of recharge to the Edwards and associated limestones in the San Antonio area during 1971 are summarized in this report. The compilation of these basic records is part of a continuing hydrologic investigation by the U.S. Geological Survey in cooperation with the Edwards Underground Water District and the Texas Water Development Board. Previous reports are given in the list of references.

The annual precipitation at selected stations throughout the San Antonio area for 1971 and the annual average for each of these stations are shown in table 1. Rainfall was above average throughout most of the recharge area during 1971.

The recorded high and low water levels in five selected key wells during 1971 are shown in table 2. During the year, the water levels reached a lower point during June than had been experienced for several years; however, toward the latter part of the year, the water levels fluctuated near the record highs. The record highs and lows are also given in table 2. Ground-water storage in the Edwards Limestone remained above average during 1971.

Recharge to the Edwards and associated limestones is chiefly from streams that lose most of their base flow and a part of their flood flow as they cross the Balcones Fault Zone on the outcrop of the aquifer. The recharge is estimated from discharge records at gaging stations located above and below the infiltration areas on most of the streams. The monthly mean discharge at the gaging stations for October-December 1971 is given in table 3. Streamflow records for January-September 1971 will be published by the U. S. Geological Survey in late 1972.

The recharge in each basin of the San Antonio area for 1971 and the average annual recharge for the period 1934-70 are given in table 4. The basic methods employed by Petitt and  George (1956) and by Garza (1962) were used for estimating the 1971 recharge. Total recharge in 1971 was in excess of the average annual recharge by nearly 400,000 acre-feet and was about 75 percent above the annual average {see table 4).

Floods resulting from high-intensity rains during August through November provided about 75 percent of the annual recharge, while the remaining recharge was provided by springflow from the Edwards Plateau.