Land-surface subsidence has been mapped in the Houston-Galveston area and is known to have occurred in other areas within the Texas coastal region. Most of the subsidence has been caused by both the withdrawal of ground water and by the production of oil, gas, and associated ground water. LAND-SURFACE SUBSIDENCE EXPLANATION 042 O LOCATION OF BENCH MARK WITH MAXIMUM TIME MECOn-NHmbw it decline I* •motto* totott. far period of record. 1*17-SI » LOCATION OF BENCH MARK WITH MIXED TIME MECORO THAT HAS A NET DECLINE IN ELEVATION MT| BENCHMARK BENTIFKATON Q SELECTED AREA OF CONCENTRATION OF WATER WELLS