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 West Branch Susquehanna River Watershed covers almost 7000 square miles in central and north-central Pennsylvania. The upper or western part of the watershed lies mainly in the Appalachian Plateau Physiographic Province and is generally characterized by narrow flat-bottomed valleys with steep walls rising to rolling plateaus. Low mountains typically range up to 2500 feet in elevation. Most of the area is forested, with numerous state parks, state forests, and state game lands. Stream gradients along the main stem West Branch Susquehanna River in this portion of the watershed average about 6 feet per mile. Some tributary streams, however, have gradients that exceed 15 to 20 feet per mile, contributing to quick increases in runoff during intense storms or rapid snowmelt events. The eastern part of the watershed lies mainly in the Ridge and Valley Physiographic Province. Stream gradients along the main stem West Branch Susquehanna River in this lower portion of the watershed flatten out and average about 2 feet per mile. Valley portions are devoted mainly to agriculture.
In addition to the West Branch Susquehanna River, major tributary streams in the watershed include Clearfield Creek, Moshannon Creek, Bald Eagle Creek, Sinnemahoning Creek, Kettle Creek, Pine Creek, Lycoming Creek, Loyalsock Creek and Muncy Creek. There are only two major population centers in the watershed. Williamsport has a population of almost 30,000 and Lock Haven has a population of almost 10,000; both cities are located on the banks of the West Branch Susquehanna River. Most other towns in the watershed have populations less than 5,000 people, with many being located adjacent to tributary streams and the main stem West Branch Susquehanna River.
The four reservoir projects in the watershed are regulated as a system for flood risk management along the West Branch Susquehanna River. Taken together, these four projects have generated over $860 million in flood damage reduction benefits over the past 50 years. Each reservoir also provides water-oriented recreational features such as beaches, boat launches, fishing facilities, camping areas, and picnic zones that are managed by state and local sponsors. Portions of the West Branch Susquehanna watershed are degraded by acid mine drainage from abandoned coal mines, and the Curwensville and Sayers projects are occasionally regulated to mitigate the adverse effects of acid mine drainage along the West Branch Susquehanna River. In addition, Curwensville Lake provides 5240 acre-feet of dedicated water supply storage for downstream consumptive use make-up.