Hydrographic Survey Program

The Hydrographic Survey Program began in 1991, when the Texas Legislature authorized the Texas Water Development Board (TWDB) to develop a non-profit, self-supporting, reservoir volumetric survey program.  The Texas Water Code authorizes TWDB to perform surveys to determine reservoir storage capacity, sedimentation levels, rates of sedimentation, and projected water supply availability.  Over time, reservoirs lose capacity due to sedimentation.  With population and statewide water use increasing, current estimates of reservoir capacity for statewide water planning purposes are essential.

A standard TWDB volumetric survey is a quick, accurate, and affordable way to get a reservoir's current capacity.  A volumetric survey report includes updated elevation-area-capacity tables and a bathymetric contour map.

While a volumetric survey only identifies the current bottom surface of a reservoir, a TWDB sedimentation survey identifies the pre-impoundment surface of the reservoir as well.  Sediment core samples are collected throughout the reservoir and correlated with multi-frequency acoustic data signal returns to aid in the identification of the pre-impoundment surface.  A sedimentation survey report includes updated elevation-area-capacity tables, a bathymetric contour map, a sediment volume and annual average sedimentation rates, and a map of sediment thicknesses throughout the reservoir.

Since 1992, the TWDB's Hydrographic Survey Program has completed 200 hydrographic surveys on 116 unique reservoirs. Repeat surveys have been completed on 57 unique reservoirs.  Of the 120 water supply reservoirs monitored for inclusion in the TWDB's monthly Water Conditions Report, the TWDB has surveyed 94.  Of the 184 total major water supply reservoirs in Texas (greater than 5,000 acre-feet in capacity) identified in the 2027 State Water Plan, 106 (58%) have been surveyed by the program.

For information on the Hydrographic Survey Program or to get your reservoir surveyed, please contact: Hydrosurvey or call (512) 936-0815