Managing Water in River and Reservoir Systems: Water Resources, Institutional Practices, and Constructed Infrastructure in Texas

Water management consists of planning, development, regulation, conservation, protection, allocation, and use of water in streams, rivers, lakes, reservoirs, aquifers, and other components of the natural and human-modified hydrologic cycle. Understanding water management in Texas requires an understanding of water management concepts in general as applied throughout the nation and world, as well as specific endeavors within Texas. Texas is a notable leader in pursuing innovative new water management endeavors that can be beneficially replicated in other states of the United States and other countries. The water management community consists of individuals and organizations with different concerns and responsibilities working together on collaborative endeavors. Water resources include precipitation, soil moisture, groundwater aquifers, and seawater, as well as water in streams and lakes. Most of the storage capacity in the numerous storage facilities throughout Texas is contained in a small number of the largest major reservoirs.

The welfare and prosperity of the citizens of Texas, like elsewhere throughout the United States, depend on the capabilities of a myriad of individuals and organizations responsible for collaboratively managing water and related land and environmental resources. The institutional framework for river and reservoir system water management is embedded within a more general water management institutional setting, which is comprised of an array of interconnected organizations, laws, policies, customs, infrastructure operational practices, and resource management strategies. The institutional framework for both water management in general and river/reservoir system water management is shaped by the four types of responsibilities. The Civil Works Program of the US Army Corps of Engineers (USACE) is the oldest and largest reservoir construction and management organization in the nation, with 537 reservoirs in operation nationwide. The Flood Control Act of 1960 authorized USACE to develop information needed by local governments to guide and regulate the use of floodplain land.

Operating plans and practices consist of policies, guidelines, and procedures for determining the quantities of water to maintain in rivers as instream flows, store and release from reservoirs, and divert for beneficial use under various conditions. For many water supply reservoirs, operations are based simply on making withdrawals or releases as necessary to meet water demands subject to water rights and contractual agreements. Reservoir projects include dams, outlet structures, pumping plants, pipelines, canals, river channel improvements, hydroelectric power plants, electric transmission facilities, recreation resources, roads, buildings, and various other components. Operating rules include dividing the total storage capacity of a reservoir into pools defined by designated water surface elevations. Flood control pool operations are based on minimizing the risk and consequences of making releases that contribute to downstream flooding, subject to the constraint of assuring that the maximum design water surface is never exceeded.

Online databases and computer-based, decision-support modeling systems play important roles in planning, development, and management of river and reservoir systems. This chapter provides a table on websites for accessing databases, decision-support software, and other information. The table also contains information on ten database or decision-support tools, their responsible agencies, and their websites in the United States. The first five databases are the National Water Information System, National Inventory of Dams, Water Management Software, Information on U. Army Corps of Engineers Fort Worth District Reservoirs, and Information on Texas Reservoirs. The last five databases are Precipitation and Reservoir Evaporation, Regional and Statewide Water Plans, Water Rights Viewer, Water Rights Analysis Package, and Water Availability Models. Water agencies in the United States are unique, compared to other countries, in their development and maintenance of extensive collections of useful information and decision-support tools publicly accessible online free of charge.

Hydrologic conditions in Texas vary greatly both spatially and temporally. This chapter explores the characteristics of precipitation, reservoir surface evaporation, and stream flow with a particular focus on variability and stationarity. River system hydrology is fundamental to the development and operation of reservoir projects and other water management endeavors. The chapter discusses natural pollution of surface stream flow from salts dissolved from underlying geologic formations that occurs in portions of the upper watersheds of several major river basins in Texas and neighboring states. The large land area of Texas encompasses multiple regions with distinct climates. Texas is viewed in this chapter as hydrologically comprising western, central, and eastern thirds. The Texas Water Development Board maintains annually updated datasets of monthly precipitation rates and monthly reservoir surface evaporation rates for 92 1-degree latitude by 1-degree longitude quadrangles comprising a grid that encompasses the state. Precipitation in Texas is mainly rainfall.

Dams and reservoirs are essential for managing hydrologic fluctuations encompassing the extremes of floods and droughts along with seasonal and continuous variability. Most reservoir projects in Texas were constructed during the 1940s through 1980s era of large-scale water resources development nationwide. This chapter explores river basin development statewide. Water availability and supply reliability throughout Texas are governed by reservoir storage capabilities and characteristics examined in the chapter. The 1950–1957 drought is the most hydrologically severe drought for much if not the majority of Texas and is at least one of the three most hydrologically severe droughts for essentially all of Texas since before 1900. The most common instream and in-lake water uses in Texas are recreation, preservation and enhancement of fish and wildlife and ecosystems, and hydroelectric power generation. Reservoir surface evaporation is a consideration in conjunctive management of supplies from reservoirs with high evaporation rates and groundwater aquifers with low or negligible evapotranspiration.

Many reservoir projects and related constructed facilities are operated throughout Texas. The water resources and facilities most important to each person are those that supply that person’s own water needs, recreational opportunities, and other services. Likewise, for water managers, the most important projects are those for which they are directly responsible. This chapter highlights selected projects that play central roles in water management in each of the river basins. The 268,600 sq. mi area of Texas is comprised of the 15 major river basins and eight coastal basins. The 15 major river basins of the state are discussed individually in the chapter. The eight coastal basins are covered as a single section. Water right permits are required prior to construction of a new reservoir project. In general, all reservoirs with conservation storage capacities of at least 200 ac-ft require water right authorization.

This chapter elaborates on the book’s exploration of water management in Texas along with summarizing and articulating conclusions. Management of water resources and constructed infrastructure of the river and reservoir systems of Texas is driven by extreme hydrologic variability, rapid population growth, depleting groundwater supplies, intensifying demands on surface water resources, and uncertainties about future hydrology and demands on water resources. Water management in the 15 major river basins and eight coastal basins of Texas is representative of water needs, problems, issues, constructed facilities, institutions, management strategies, and practices throughout the United States and other countries. Texas encompasses all or portions of 15 major river basins and all of eight coastal basins located between the lower reaches of the major river basins. Reservoir projects in Texas are accompanied by major conveyance facilities comprised in several cases of more than a hundred or even several hundred miles of pipeline and associated pumping stations to transport water to cities.