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 197 hydrographic surveys on 114 unique reservoirs (as of August 2021).  This includes 89 of the 118 water supply reservoirs monitored for inclusion in the TWDB's monthly Water Conditions Report.  Combined, these 118 reservoirs represent 96% of the total conservation storage capacity of the 188 major water supply reservoirs in Texas.  By definition, a major reservoir has a conservation storage capacity of 5,000 acre-feet or greater.

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