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.