USACE CWMS - Chehalis 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 Wynoochee River basin is 195 square miles and located on the Olympic Peninsula in the State of Washington. It is one of several tributaries feeding the Chehalis River before it drains at the mouth of Grays Harbor. The basin extends about 40 miles in the north-south direction and about 5 miles in the east-west direction.
The Wynoochee River flows 68 miles from its headwaters on the southern slopes of the Olympic Mountains to the Chehalis River. For the first 8 miles, Wynoochee River drops in elevation from nearly 5,000 feet to 1,000 feet then flows 16 miles through a forested valley known as the Weatherwax basin. Wynoochee Dam is located midway through the Weatherwax basin and regulates flows from about one quarter of the drainage area above the control point, Wynoochee River above Black Creek. USACE is authorized to use flood control storage in the reservoir at Wynoochee Dam.
Below the Weatherwax basin the river travels 4 miles through a twisting canyon, then winds 13 miles among gravel bars confined by steep valley slopes. The lower 27 miles of the river meanders through pastures and hayfields. Upstream of the dam tributaries are small. Downstream, the larger tributaries are Big Creek (9.7 square miles), Schafer Creek (12.9 square miles), and Black Creek (25.1 square miles).
The upper basin has rugged mountains and is not populated. The lower basin is primarily agricultural and is sparsely populated with houses and barns. The City of Montesano (population 4,000), is the only city within the basin and has the largest potential for economic damages or threat to life safety in a large flood event.
The agricultural area of the Wynoochee valley consists of 3,980 acres in the flood plain along the lower 27 miles of the river. These bottom lands are among the most productive of Grays Harbor County. Cultivated land is used for feed crops, primarily hay and silage, with clover and timothy hay the most common types. There are few major developments along the river. The city of Aberdeen has an industrial water intake at RM 8.1; there is a commercial gravel pit operation at RM 3.2; US Highway 410 crosses at RM 2.7; and the North Pacific Railroad crosses at RM 1.6.

Corps 水资源管理系统（CWMS）包含四个相互关联的模型，旨在协助对该流域的水资源进行管理：
- GeoHMS（地理空间水文建模扩展）
- ResSIM（水库系统模拟）
- RAS（河流分析系统）
- FIA（洪水影响分析）

Wynoochee 河流域面积达 195 平方英里，位于华盛顿州奥林匹克半岛。它是数条汇入 Chehalis 河并在 Grays Harbor 河口排入海洋的支流之一。该流域在南北方向延伸约 40 英里，在东西方向延伸约 5 英里。

Wynoochee 河从奥林匹克山脉南坡的源头流向 Chehalis 河全程 68 英里。在前 8 英里，Wynoochee 河从近 5,000 英尺的高程降至 1,000 英尺，然后流经一个被称为 Weatherwax 盆地的森林谷地，全程 16 英里。Wynoochee 水坝位于 Weatherwax 盆地中部，并调节来自控制点以上约四分之一流域面积的水流，该控制点位于 Black Creek 上游的 Wynoochee 河之上。美国陆军工程兵团（USACE）被授权在 Wynoochee 水坝的水库中储存洪水控制用水。

Weatherwax 盆地以下，河流蜿蜒穿过 4 英里的曲折峡谷，然后沿着陡峭的山谷斜坡间的砾石滩蜿蜒 13 英里。河流下游的 27 英里穿过牧场和干草地。在坝上游，支流较小；在坝下游，较大的支流包括 Big Creek（9.7 平方英里）、Schafer Creek（12.9 平方英里）和 Black Creek（25.1 平方英里）。

上游流域地形崎岖，无人居住。下游流域以农业为主，人口稀少，仅有房屋和谷仓。Montesano 市是该流域内唯一的城市，人口约 4,000，在大型洪水事件中具有最大的经济损失或生命安全威胁潜力。

Wynoochee 盆地的农业区域位于河流下游 27 英里处的洪泛区，总面积为 3,980 英亩。这些河漫滩是该县最为肥沃的土地之一。耕作土地主要用于饲料作物，主要是干草和青贮饲料，其中三叶草和 Timothy 干草最为常见。河流沿线很少有重大开发。Aberdeen 市在 RM 8.1 处设有工业用水取水口；在 RM 3.2 处有商业砾石开采作业；US Highway 410 在 RM 2.7 处穿过；North Pacific 铁路在 RM 1.6 处穿过。