USACE CWMS - Ouachita 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)
The Ouachita River rises in the Ouachita Mountains near Mena, Polk County, Arkansas, and flows southeasterly for about 605 miles through Arkansas and Louisiana. It flows into the Red River about 35 miles above the confluence with the Mississippi River. The Ouachita, Tensas, and Little Rivers form the Black River at Jonesville, LA 57 miles above its confluence with the Red River. The Ouachita River drains some 24,200 square miles, of which, 1,105 square miles are above Blakely Mountain Dam.
The Ouachita River basin may be divided into three topographic sections called mountain, hill, and delta. The mountain section comprises 15 percent of the total area and lies in the upper reaches of the Ouachita River and its tributaries. In this section the terrain is rugged, composed of parallel ridges separated by deep valleys with elevations ranging from 400 to 2,000 feet above mean sea level. The area is timbered, except in the narrow valleys which are farmed to a small extent. The mountainous section extends from the headwaters to about Malvern, AR which is about 334.4 miles above the mouth of the Black River. The hill section, which includes 55 percent of the total drainage area, extends along the main stream from Malvern, AR to Moro Bay, AR which is mile 229.6. This area is rolling and hilly except for the flat bottom land along the river. Below Moro Bay, the river enters the alluvial valley and traverses bottom lands dissected by numerous swamps, lakes, and bayous. The delta section includes the remaining 30 percent of the total Ouachita River drainage area. The Ouachita River below Columbia Lock and Dam (mile 117.8) lies in the Red-Ouachita backwater area. The principal Ouachita River tributaries, between Blakely Mountain Dam and Moro Bay, are Caddo River, drainage area 490 square miles, entering the river above Arkadelphia, AR, at mile 426; Little Missouri River, drainage area 2,080 square miles, entering between Arkadelphia and Camden, AR at mile 380; and Smackover Creek, drainage area 526 square miles, entering the river at mile 313. River slopes average 12 feet per mile in the first 80 miles from the source and 4 feet per mile in the next 80 miles, while from Malvern, AR to Moro Bay they decrease from 2.5 to 0.4 feet per mile. Channel dimensions vary from a trace at the source to widths of 300 feet near Malvern and 800 feet near Moro Bay with bank heights of 15 to 25 feet.

The Corps Water Management System (CWMS) 聚合了四个相互关联的模型，旨在辅助流域的水资源管理：
- GeoHMS（地理水文建模扩展）
- ResSIM（水库系统模拟）
- RAS（河流分析系统）
- FIA（洪水影响分析）

奥查塔河源于阿肯色州波克县梅纳附近的奥查塔山脉，向东南方向流淌约605英里，穿越阿肯色州和路易斯安那州。河流在距密西西比河交汇点上游约35英里的地方汇入红河。奥查塔河、滕萨斯河和利特尔河在路易斯安那州琼斯维尔上游57英里处汇合形成布莱克河。奥查塔河流域总面积约为24,200平方英里，其中1,105平方英里位于布莱克利山坝以上。

奥查塔河流域可划分为三个地形区，分别为山区、丘陵区和三角洲区。山区占总面积的15%，位于奥查塔河及其支流的上游。在该区域，地形崎岖，由平行山脉和深谷组成，海拔高度介于海平面以上400至2,000英尺之间。该区域以森林为主，除狭窄的山谷外，山谷被少量耕作。山区从源头延伸至阿肯色州马尔文，大约位于布莱克河河口上游334.4英里处。丘陵区占总排水面积的55%，沿主河道从阿肯色州马尔文延伸至莫罗湾，约为229.6英里。该区域地形起伏，除了河流沿岸的平坦地带外。莫罗湾以下，河流进入冲积谷，穿越被众多沼泽、湖泊和溪流切割的平原。三角洲区涵盖了奥查塔河流域剩余的30%。

奥查塔河在哥伦比亚水闸和坝（117.8英里）以下位于红-奥查塔回水区。奥查塔河的主要支流，从布莱克利山坝至莫罗湾之间，包括卡多河，排水面积为490平方英里，在阿肯色州阿卡迪亚上游426英里处汇入河流；小密苏里河，排水面积为2,080平方英里，在阿肯色州阿卡迪亚和坎登之间380英里处汇入河流；以及斯马克弗里克溪，排水面积为526平方英里，在313英里处汇入河流。河流坡度在前80英里内平均为每英里12英尺，在接下来的80英里内为每英里4英尺，从阿肯色州马尔文至莫罗湾则从每英里2.5英尺降至0.4英尺。河槽尺寸从源头的一丝不苟到马尔文附近的300英尺以及莫罗湾附近的800英尺不等，河岸高度为15至25英尺。