USACE CWMS - Brazos River Watershed

The Corps Water Management System (CWMS) includes four interrelated models to assist with water management for the basin:

- GeoHMS (Geospatial Hydrologic Modeling Extension)
- ResSIM (Reservoir System Simulation)
- RAS (River Analysis System)
- FIA (Flood Impact Analysis)

Lake where it flows in a southeasterly direction to empty into the Gulf of Mexico near Freeport, Texas. The Brazos River is the 11th longest river in the United States flowing 1,280 miles. The Brazos River and its principal tributaries Clear Fork Brazos River, Aquilla Creek, Bosque River, Leon River, Lampasas River, Little River, San Gabriel River, Navasota River, and Yegua Creek flow through mostly rural and agricultural areas. The largest urban areas are Waco, Belton, Georgetown, Richmond, and Freeport. The total drainage area of the Brazos River basin is approximately 45,625 square miles. The precipitation varies from west to east and from the north to south portions of the basin. The upper Brazos from the west to the east receives 15 – 30 inches, and from the upper to lower receives 30 – 45 inches, on average, each year. The basin, particularly in the southern basin, can experience extremely intense precipitation events capable of producing staggering rainfall totals. These systems range from intense thunderstorms to hurricanes.

The climate of the Brazos watershed varies considerably from temperate to subtropical. The average annual temperature is 59°F in its upper reaches and 70° in the coastal region. Normally, the winters are mild and short, even in the upper reaches, but severe weather is not unknown. Temperatures of zero and even lower have been recorded. The average annual rainfall is 29.5 inches, ranging from sixteen in the northwest to forty-seven in the southeast. Soil types along the Brazos vary from sandy loams to deep clay. A variety of natural vegetation ranges from scattered oak mottes and bunch grasses in drier areas to conifers and hardwoods in areas where rain is plentiful. Virtually the entire area of the watershed is suitable for some form of farming or ranching activity. The most important products of the region have been cotton, cattle, and oil.

Many reservoirs were constructed in the Brazos Basin, and they are managed for flood control, water supply, recreation, and other uses. Brazos River Authority (BRA) is the primary entity that manages surface water in the Brazos Basin. BRA has water supply contracts with USACE in all nine USACE reservoirs; Lake Whitney, Aquilla Lake, Waco Lake, Proctor Lake, Belton Lake, Stillhouse Hollow Lake, Georgetown Lake Granger Lake, and Somerville Lake. Additionally BRA operated three large water supply reservoirs that have impacts on USACE Water Management Operations; Possum Kingdom Lake, Lake Granbury, and Lake Limestone.

During non-flood control operation, the USACE reservoirs are operated for water supply requests from BRA. During flood control operations, the USACE reservoirs are operated to multiple downstream USGS gages to provide a balanced system approach of the USACE flood storage and the local water supply reservoir releases. Priority is first given to the local water supply reservoir releases at the downstream USGS gage locations.

The Brazos River supports Dow Chemical, one of the largest manufacturers of chemicals and plastics in the world. Dow has senior water rights on the Brazos to 48 billion gallons of water a year. In recent drought years Dow has requested Texas Commission on Environmental Quality (TCEQ) to suspend the junior rights of farmers, municipalities, and other users upstream to ensure their water demands are met.

军团水资源管理系统（Corps Water Management System, CWMS）包含四个相互关联的模型，用于辅助该流域的水资源管理工作：
- 地理空间水文模拟扩展（Geospatial Hydrologic Modeling Extension, GeoHMS）
- 水库系统模拟（Reservoir System Simulation, ResSIM）
- 河道分析系统（River Analysis System, RAS）
- 洪水影响分析（Flood Impact Analysis, FIA）

布拉索斯河向东南方向汇入墨西哥湾，入海口位于德克萨斯州弗里波特（Freeport）附近。布拉索斯河（Brazos River）是美国第11长河流，全长1280英里。布拉索斯河及其主要支流包括布拉索斯河北支、阿奎拉溪、博斯克河、利昂河、拉帕萨斯河、利特尔河、圣加布里埃尔河、纳瓦索塔河以及耶瓜溪，其流域内多为乡村与农业区域。流域内主要城市包括韦科、贝尔顿、乔治敦、里士满以及弗里波特。布拉索斯河流域总面积约为45625平方英里。流域内降水量自西向东、自北向南均存在差异：流域上游区域自西向东的年均降水量为15至30英寸，上游至下游区域的年均降水量则为30至45英寸。南部流域尤其容易发生极端强降水事件，可带来惊人的降雨总量，此类天气系统涵盖强雷暴与飓风。

布拉索斯流域的气候差异显著，从温带气候至亚热带气候均有分布。流域上游年均气温为59华氏度，沿海区域则为70华氏度。通常情况下，即便在流域上游，冬季也温和短促，但极端天气亦时有发生，曾记录到零摄氏度及以下的低温。流域年均降水量为29.5英寸，西北部区域最低为16英寸，东南部区域最高可达47英寸。布拉索斯河流域的土壤类型从砂壤土至深层黏土不等。自然植被种类丰富，干旱区域以零散的橡树林丛与丛生禾草为主，降水充沛区域则以针叶林与硬木林为主。流域内几乎所有区域均可开展各类农牧业活动，该区域最重要的物产为棉花、肉牛与石油。

布拉索斯流域内建有多座水库，其管理目标涵盖防洪、供水、休闲娱乐及其他用途。布拉索斯河管理局（Brazos River Authority, BRA）是布拉索斯流域地表水管理的主要责任主体。BRA与美国陆军工程兵团（United States Army Corps of Engineers, USACE）签订了9座USACE水库的供水合同，分别为惠特尼湖、阿奎拉湖、韦科湖、普罗克特湖、贝尔顿湖、斯蒂尔豪斯霍洛湖、乔治敦湖、格兰杰湖以及萨默维尔湖。此外，BRA还运营三座对USACE水资源管理运营存在影响的大型供水水库：负鼠王国湖、格拉伯里湖以及莱姆斯通湖。

在非防洪调度期间，USACE水库将按照BRA的供水需求进行调度。在防洪调度期间，USACE水库将配合下游多个美国地质调查局（United States Geological Survey, USGS）水文站，采用平衡USACE防洪库容与地方供水水库泄流的系统调度方案。调度优先级首先保障下游USGS水文站处的地方供水水库泄流需求。

布拉索斯河为陶氏化学（Dow Chemical）提供水源，该公司是全球规模最大的化工与塑料制品制造商之一。陶氏化学在布拉索斯河拥有每年480亿加仑水量的优先水权。近年来的干旱年份中，陶氏化学曾请求德克萨斯州环境质量委员会（Texas Commission on Environmental Quality, TCEQ）暂停上游农户、市政当局及其他用户的次级水权，以保障自身用水需求得到满足。