Fort Bend County Surface Water Supply Study Phases 1 and 2
Total Page:16
File Type:pdf, Size:1020Kb
- Fort Bend County - Surface Water Supply Study - Phases 1 and 2 - Prepared for: .. Fort Bend County Surface Water Supply Corporation - \ - \ - - - - - by - A Joint Venture of - Lichliter/Jameson & Associates, Inc. and ... Turner Collie & Braden, Inc. - January, 1993 FORT BEND COUNlY SURFACE WATER SUPPLY STUDY PHASES 1 AND 2 PREPARED FOR FORT BEND COUNTY SURFACE WATER SUPPLY CORPORATION BY A JOINT VENTURE OF UCHLfTER/JAMESON & ASSOCIATES, INC. AND TURNER COWE & BRADEN INC. January, 1993 ... ... ... - .. • Fort Bend County Surface Water Supply Study Phase 1 FORT BEND COUNTY SURFACE WATER SUPPLY STUDY PHASE 1 SECTION I INTRODUCTION GENERAL PURPOSE AND OBJECTIVES SECTION II BACKGROUND GENERAL STUDY AREA SECTION III PREVIOUS LOCAL AND REGIONAL FACILITIES PLANNING STUDIES GENERAL A REGIONAL WATER SUPPLY PLANNING STUDY FOR THE HARRIS GALVESTON COASTAL SUBSIDENCE DISTRICT REGIONAL WATER SUPPLY STUDY FOR THE CITIES OF RICHMOND AND ROSENBERG AND SURROUNDING AREAS REGIONAL WATER SUPPLY AND WASTEWATER TREATMENT FACILITIES FOR THE BRAZOS BEND WATER AUTHORITY REGIONAL WATER SUPPLY AND PLANNING STUDY FOR FORT BEND WC 10 NO.2 AND SUGAR LAND WEST HARRIS COUNTY SURFACE WATER SUPPLY CORPORATION: IMPLEMENTATION PLAN CITY OF HOUSTON WATER MASTER PLAN CONCLUSIONS FROM THE PREVIOUS STUDIES SECTION IV EXISTING WATER SUPPLY FACILITIES GENERAL SOURCES OF WATER WATER RIGHTS FROM THE TEXAS WATER COMMISSION PUBLIC WATER SUPPLY ENTITIES IN FORT BEND COUNTY EXISTING WATER UTILITY RATES SECTION V PROJECTIONS OF WATER USE GENERAL EXISTING POPULATION EXISTING LAND USE HISTORICAL WATER USE IN FORT BEND COUNTY PROJECTION OF GROWTH IN POPULATION AND WATER DEMAND SECTION VI IMPACTS OF CONTINUED GROUNDWATER USE GENERAL IMPACTS OF CONTINUED GROUNDWATER WITHDRAWAL WATER QUALITY IMPACTS ON EXISTING WATER PRODUCTION FACILITIES EXHIBITS EXHIBIT 11-1 STUDY AREA EXHIBIT 111-1 PREVIOUS STUDY AREAS & ALLEN'S CREEK RESERVOIR EXHIBIT IV-1 GULF COAST AQUIFER SYSTEM PROFILE EXHIBIT IV-2 WATER SOURCES AND WATER ENTITIES EXHIBITV-1 FORT BEND COUNTY LAND USE EXHIBITV-2 WATER DEMAND COMPARISON EXHIBITV-3 POPULATION PROJECTION FOR FORT BEND COUNTY EXHI BIT VI-1 FAULT AND SALT DOMES IN FORT BEND COUNTY EXHI BIT VI-2 POTENTIOMETRIC LEVEL DECUNES IN FORT BEND COUNTY (1990 - 2030) EXHIBIT VII-1 LAND SURFACE SUBSIDENCE FORT BEND COUNTY, TEXAS EXHIBIT VII-2 TYPICAL STREAM IMPACT OF SUBSIDENCE EXHIBIT VII-3 PANEL 1 - AERIAL VIEW OF DECEMBER 1991 FLOOD AND FEMA 100-YEAR FLOOD PLAIN EXHIBIT VII-4 PANEL 2 - AERIAL VIEW OF DECEMBER 1991 FLOOD AND FEMA 100-YEAR FLOOD PLAIN EXHIBIT VII-5 PANEL 3 - AERIAL VIEW OF DECEMBER 1991 FLOOD AND FEMA 100-YEAR FLOOD PLAIN EXHIBIT VII-6 PANEL 4 - AERIAL VIEW OF DECEMBER 1991 FLOOD AND FEMA 100-YEAR FLOOD PLAIN EXHIBIT VII-7 DEPTH - FREQUENCY CURVE FORT BEND COUNTY SURFACE WATER SUPPLY STUDY PHASE 1 SECTION I - INTRODUCTION GENERAL Fort Bend County has long recognized the need to manage its water resources, which to date is comprised of groundwater for public supply and a combination of groundwater and surface water for other uses. The county now has in place a county-wide subsidence district which is currently developing a plan to regulate groundwater withdrawal. It is anticipated that as the county continues to grow, limitations will be placed on the usage of groundwater to control subsidence and to more effectively utilize the county's groundwater resources. Technical information is needed to identify what the potential impacts of subsidence are in terms of increased flood damage, so that appropriate decisions may be made regarding the need and timing of conversion to surface water. If limitations are placed on groundwater usage, alternative supplies from surface water sources must be developed if the county is to continue to grow. A water supply technical and management plan for the entire county must be developed to identify cost-effective solutions to the current and future water needs of Fort Bend County. Several previous studies in the Fort Bend County area, some of which were partially funded through the Texas Water Development Board (TWDB) planning grants, have been performed to develop plans for conversion of specific political subdivisions to surface water. These studies were performed before the Fort Bend County Subsidence District (FBCSD) was created. Generally these studies have started with the assumption that specific areas must convert to surface water and then have proceeded to develop individual plans for conversion. No analysis has been performed in these studies to determine the impact of subsidence on flooding and to determine specifically where and when conversion to surface water is necessary. These individual plans may not be the most cost-effective and economical approach to provide surface water if and when it is needed. Also, if a more regional approach were taken with regard to groundwater withdrawal, certain areas that have been recommended for conversion may not need to convert to surface water at least for long periods of time. Because of these factors, it was proposed that this study be performed to address on a broader scale the question of when and where conversion to surface water should occur. In November of 1990, Fort Bend County petitioned to the Texas Water Development Board for a planning grant to develop a regional water supply plan. To organize the regional planning approach and to I - 1 SECTION II - BACKGROUND GENERAL The population In Fort Bend County increased from 130,846 to 225,421 between 1980 and 1990. In 1990 municipal water demand comprised 37.0 million gallons per day (mgd) , obtained almost exclusively from groundwater. The Gulf Coast aquifers under1ying Fort Bend County currently supply all municipal demand in the County as well as most irrigation, agriculture, and industrial demands. The overall rate of groundwater withdrawal in the Houston, Texas area, including Fort Bend County, has resulted in the lowering of potentiometric levels, or the water table in an aquifer under pressure, and the consolidation of underlying clay layers within the aquifers. This compaction has resulted in land subsidence of as much as three feet in some of the most populous areas in Fort Bend County in the period from 1964 to 1990. Declining potentiometric levels has resulted in land subsidence which has contributed to increased flooding, ground faulting, and deterioration in water quality in other portions of the region, particularly the coastal areas along Galveston Bay in eastem Harris and Galveston Counties. The projected increase in water demand combined with the history of subsidence has resulted in a growing concern about future water supplies in Fort Bend County. In 1989, the Texas Legislature established the Fort Bend Subsidence District to manage the groundwater resources in the County. This agency has focused on developing an inventory of groundwater wells and establishing a permitting procedure for all wells greater than five inches in diameter. However, no single entity in Fort Bend County exists to coordinate the county's water supplies for future growth. STUDY AREA The planning area for this study coincides with the geographical boundary of Fort Bend County in southeast Texas, as shown on Exhibit 11-1. The county encompasses approximately 876 square miles and includes the cities of Arcola, Fulshear, Kendleton, Meadows, Missouri City, Needville, Orchard, Pleak, Richmond, Rosenberg, Simonton, Stafford, and Sugar Land. Also included are the towns of Beasley and Thompson, various municipal utility districts, and portions of the cities of Houston and Katy, which lie within Fort Bend County. The planning area generally lies in the Brazos River Basin. The San Bernard River forms the southwestern boundary and also drains part of the county. In addition, a small portion of eastern Fort Bend County drains to the San Jacinto River. Soils vary from rich alluvium in the flood plain of the Brazos River to black, sandy loam, and clay on the prairies. Fort Bend County has ground surface elevations that range from 46 II - 1 MAP SOURCE: TEXAS DEPARTMENT OF TRANSPORTATION OFFICIAL HIGHWAY TRAVEL MAP. (19901 EXHIBIT 11-1 STUDY AREA FORT BEND COUNTY SURFACE WATER SUPPLY CORPORATION LICHLITERfJAMESON & ASSOCIATES, INC. o 25 TURNER COLLIE & BRADEN INC. SCALE IN MILES DATE: JUNE 1992 JOB NO. 33-0736-1000 --_._-------_... SECTION III - PREVIOUS LOCAL AND REGIONAL FACIUTY PLANNING STUDIES GENERAL Conversion from groundwater to surface water as the primary source of water supply for municipal needs has been viewed as the most viable option to reduce the county's dependence on groundwater. Previous studies in and around Fort Bend County have addressed the feasibility of implementing surface water conversion. These studies focused on service areas delineated by the limits of political jurisdiction of cities or districts. This approach has resulted in four separate plans serving the areas shown on Exhibit 111-1. The following paragraphs describe these previous water supply planning studies pertinent to Fort Bend County. A REGIONAL WATER SUPPLY PLANNING STUDY FOR THE HARRIS-GALVESTON COASTAL SUBSIDENCE DISTRICT In 1989, Harris-Galveston Coastal Subsidence District (HGCSD) initiated a study that projected the quantity and spatial distribution of water demands for the 13-county planning area surrounding Houston, Texas through year 2030. The planning area included Fort Bend County. Although the HGCSD examined the water needs in the 13 county areas in order to access the potential impact on water levels in the aquifer and resulting ground subsidence, its enabling legislation limits its regulatory authority to Harris and Galveston counties. Consequently, its detailed regulatory action plan, which calls for the transition from groundwater to surface water, is based solely on its ability to require this conversion within its jurisdiction, without regard to what is happening outside of its jurisdiction. In evaluating alternatives for water supply planning for Harris and Galveston Counties, the HGCSD examined the potential impact on land subsidence if all future water demand through the year 2030 was to be supplied through groundwater production.