Shifting to surface water

Where does your water come from? Most people will answer -- the faucet. But before your faucet – where does your water come from?

There are two types of water that could come to your faucet; surface water and ground water. Surface water, comes from lakes, rivers and streams flowing above ground. Groundwater, or what many people call “well water,” is water that is obtained by drilling a hole in the earth and extracting the stores of underground water.

As Texas’ population continues to grow, the demand for water has grown proportionately. Each year, Texans consume more than 16 million acre feet of water. An acre foot is approximately 325,851 gallons of water. About 60 percent of Texas’ residents obtain their water from groundwater sources.

However, reliance on groundwater will soon begin to decline in some parts of Texas as a result of state legislation mandating reduction of the use of groundwater due to subsidence.

What is subsidence?

Land subsidence occurs when large amounts of groundwater are removed and water pressures are reduced in the materials forming the aquifer. Aquifers that suffer subsidence are typically formed from layers of clay, sand, and gravel. When water pressures are reduced, the materials in the aquifer tend to settle and compress into less space slowly lowering the elevation of entire areas by several feet.

According to the United States Geological Service (USGS), subsidence is a global problem and is found in 45 states in the U.S. In Texas, areas near Houston, Galveston and El Paso have all experienced major subsidence of land caused by overdrawing of groundwater supplies. However, not all aquifers are subject to subsidence.

In the Brazos River basin, Fort Bend and Brazoria County’s have experienced the effects of subsidence. As a result, in 1989 the Texas Legislature created the Fort Bend Subsidence District.

The goal of the district is to slowly wean the county from reliance on groundwater stores by switching to surface water or implementing the use of water conversion through reuse.

So, why not just switch to surface water?

Unfortunately, a change from groundwater to surface water is not a simple or inexpensive process due to the costs associated with treatment.

Before either surface or groundwater travels to your faucet, it is put through a treatment process to remove bacteria and solids. For groundwater, this process is much simpler and much less costly since water stored underground has already gone through a natural filtering process as it travels through the soil and rock in the ground.

Surface water, as any Texan will tell you, is murky and usually presents a color similar to the soil in the area. In order to make surface water potable or drinkable, additional treatment is necessary.

To aid in Fort Bend’s conversion to surface water, the Brazos River Authority (BRA) initiated a preliminary engineering study to look into the possibility of establishing a regional surface water treatment plant in western Fort Bend County. The regional plant could serve the cities of Richmond and Rosenberg, Pecan Grove Municipal Utility District (MUD) and Fort Bend MUD 25. The regional plant would allow the district to reduce their use of groundwater by 30 percent by 2013 and 60 percent by 2025.

During the next year, the BRA and the stakeholder cities and utilities will conduct water quality testing that will aid in establishing criteria for the design of the future plant.