Brazos River Alluvium Aquiferinteractive map

Summary

The Brazos River Alluvium Aquifer is a minor aquifer found along the Brazos River in east-central Texas. The aquifer is as much as 7 miles in width and extends along 350 river miles from southern Bosque County to eastern Fort Bend County. Groundwater is contained in alluvial floodplain and terrace deposits, although the latter is not an appreciable source of water. The floodplain alluvium consists of fine to coarse sand, gravel, silt, and clay. These deposits have a complex geometry, with beds or lenses of sand and gravel that pinch out or grade vertically into finer material. In general, finer sediments occur in the upper part of the aquifer, and coarser material is in the lower part. The thickness of the aquifer ranges from negligible to 168 feet, with an overall average of about 50 feet.

Water in the aquifer is very hard and fresh to slightly saline, generally containing less than 1,000 milligrams per liter of total dissolved solids but ranging to as much as 3,000 milligrams per liter in some wells. The aquifer is under water table conditions in most places and is used mainly for irrigation. The water table generally slopes toward the Brazos River, this direction indicating that the river is a gaining stream in most places.

Recharge to the aquifer occurs from rainfall on the aquifer and subsequent downward leakage to the saturated zone. Discharge from the aquifer occurs through evapotranspiration, discharge to the river, and withdrawals from wells. Some wells can yield as much as 1,000 gallons per minute, but the majority of wells yield from 250 to 500 gallons per minute. No significant water level declines have occurred in the aquifer.

Reports