USACE CWMS - Boise 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)

The watershed is composed largely of precipitous mountains, and as a whole, is characterized by a highly dissected topography with deep V-shaped valleys, steep slopes, and narrow and sharp top ridges. The topography becomes increasingly rough toward the eastern boundary. The basin above Lucky Peak dam ranges in elevation from 3,000 to 10,500 feet. The mean elevation of the basin is 5,800 feet. The mean annual average precipitation for the basin ranges from 8 inches in the lower basin to 55 inches at the highest elevations; the value at Lucky peak dam is 15 inches.

The principal tributaries of the Boise River and their respective drainage areas are the South Fork, 1,314 square miles; Middle Fork and North Fork, 830 square miles; and Mores Creek, 426 square miles. These four tributaries comprise 97 percent of the drainage area above the Lucky Peak dam.

Major floods are typically categorized as “Winter” or “Spring” floods. Both floods usually have rainfall and snowmelt components. Winter floods are typically less duration and volume than spring floods. During winter the reservoirs are drafted down to allow space for flood events and there are no irrigation demands. In late spring the reservoirs are being filled to meet “refill requirements” for irrigation by following rule curves. Rule curves define required system flood control spaces as functions of date and operations runoff volume forecasts. A large rainfall system in conjunction with final filling of the reservoirs causes the largest risk to flood flows downstream of the reservoir system.

There are three reservoirs in the drainage area above Lucky Peak Dam; namely, Little Camas, Anderson Ranch, and Arrowrock. Little Camas Reservoir is located 22 miles northeast of Mountain Home, Idaho, on Camas Creek, a tributary of South Fork Boise River. The reservoir has a usable capacity of about 22,000 acre-feet, which is used exclusively for irrigation. This reservoir has no value for flood control and is not considered for USACE operations. Therefore, Little Camas Dam will not be modeled in HMS or ResSim. Anderson Ranch Reservoir is about 30 miles northeast of Mountain Home, Idaho, on the South Fork Boise River. The reservoir has a usable capacity of 418,000 acre-feet, which is joint use for flood control and irrigation. Arrowrock Reservoir, built by the U.S. Bureau of Reclamation for irrigation purposes, is about 22 miles east of Boise, Idaho, on the Boise River below the confluence of the South Fork and the main Boise River. The reservoir has a usable capacity of 286,000 acre-feet, which is joint use for flood control and irrigation. Lucky Peak Reservoir is about 10 miles east of Boise, Idaho, on the Boise River below the confluence of Mores Creek and the Boise River. The reservoir has a useable capacity of 264,000 acre-feet, which is joint use for flood control and irrigation.

The Lucky Peak Dam, built by the U.S. Army Corps of Engineers, is a multi-purpose dam located 9 miles southeast of Boise, Idaho, on the Boise River. The spillway is located south of the da, it is 600 feet long, has training wall abutments at each end, is made of reinforced concrete, and has an ogee shape with an apron on the downstream side. The crest of the spillway is at elevation 3063.3. Discharge over the spillway is uncontrolled and travels over the unlined open hillside to the river below the project structures. At a maximum design pool elevation of 3075.3, approximately 93,300 cfs would be passed over the spillway. The spillway is for emergency use only and should never be used for normal operations, since use of the spillway is expected to severely erode the unlined hillside below the spillway. To prevent overtopping the spillway, either accidentally or by wave action, the reservoir pool must be maintained at elevations below 3063.3.

美国陆军工程兵团水管理系统（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管理工作：
- GeoHMS（地理空间水文模拟扩展工具，Geospatial Hydrologic Modeling Extension）
- ResSIM（水库系统模拟工具，Reservoir System Simulation）
- RAS（河道分析系统，River Analysis System）
- FIA（洪水影响分析工具，Flood Impact Analysis）

该流域以陡峭山地为主，整体地貌高度切割破碎，发育有深切V型谷、陡坡与狭窄尖锐的山脊，往东边界方向地形愈发崎岖。拉基峰大坝以上流域的海拔范围为3000至10500英尺，流域平均海拔为5800英尺。流域年均降水量从下游流域的8英寸至高海拔区域的55英寸不等，拉基峰大坝处的年均降水量为15英寸。

博伊西河的主要支流及对应流域面积分别为：南支流（South Fork），1314平方英里；中支流与北支流（Middle Fork和North Fork），830平方英里；莫尔斯溪（Mores Creek），426平方英里。上述四条支流的流域面积占拉基峰大坝以上总流域面积的97%。

大型洪水通常分为“冬季洪水”与“春季洪水”两类，两类洪水均通常兼具降雨与融雪补给成分。冬季洪水的持续时长与洪量通常小于春季洪水。冬季期间，水库会预泄腾库以应对洪水事件，且无灌溉用水需求。晚春时节，水库需按照调度曲线进行蓄水，以满足灌溉的“补水要求”。调度曲线定义了系统所需的防洪库容，其为日期与运营径流量预报的函数。若遭遇强降雨天气系统且恰逢水库完成蓄水，则会对水库系统下游的河道行洪造成最大风险。

拉基峰大坝以上流域内共有三座水库，分别为小卡马斯水库（Little Camas Reservoir）、安德森牧场水库（Anderson Ranch Reservoir）与阿罗罗克水库（Arrowrock Reservoir）。
小卡马斯水库位于爱达荷州芒廷霍姆东北22英里处的卡马斯溪——博伊西河南支流的一条支流——之上，有效库容约为22000英亩-英尺，仅用于灌溉，不具备防洪功能，也未纳入美国陆军工程兵团的调度考量范围，因此HMS与ResSim不会对小卡马斯大坝进行建模。
安德森牧场水库位于爱达荷州芒廷霍姆东北30英里处的博伊西河南支流之上，有效库容为418000英亩-英尺，兼具防洪与灌溉双重用途。
阿罗罗克水库由美国垦务局修建，用于灌溉，位于爱达荷州博伊西以东22英里处的博伊西河干流——南支流与博伊西河干流汇流点下游——之上，有效库容为286000英亩-英尺，兼具防洪与灌溉双重用途。
拉基峰水库位于爱达荷州博伊西以东10英里处的莫尔斯溪与博伊西河汇流点下游的博伊西河之上，有效库容为264000英亩-英尺，兼具防洪与灌溉双重用途。

拉基峰大坝由美国陆军工程兵团修建，是一座多功能大坝，位于爱达荷州博伊西东南9英里处的博伊西河之上。溢洪道位于大坝南侧，全长600英尺，两端设有导流墙基础，采用钢筋混凝土结构，呈奥格（ogee）曲线形，下游侧设有消力池。溢洪道堰顶高程为3063.3。溢洪道泄流不受控，水流会经由未衬砌的开阔山坡流至工程结构下游的河道。在最大设计库水位3075.3时，溢洪道的泄流量约为93300立方英尺每秒（cfs）。溢洪道仅可用于应急工况，严禁用于常规调度，因为使用溢洪道会严重侵蚀溢洪道下方的未衬砌山坡。为防止溢洪道被意外漫顶或因波浪作用漫顶，水库水位必须维持在3063.3高程以下。