The major rivers within the District are the Salmon, Snake, and Clearwater. The District includes over 290 miles of streams with the majority listed on the EPA 303(d) water quality limited stream list. The 155 acres of lakes include Soldier’s Meadow Reservoir, Mann’s Lake, Waha Lake, and Blue Lake. Water quantity can be a resource issue. Runoff and flooding occur from February through May. 1996 and 1997 were years with 75 to 100 year flood events. Surface water flows tend to be the greatest in May then decrease to minimal levels over the course of the summer. Local communities obtain their water from ground and surface water systems. Lewiston obtains most of its domestic water from the Clearwater River. The City of Peck obtains its water from Big Canyon Creek. The remainder of the communities use ground water sources. Rural residents use mainly groundwater sources.

The District is within the Clearwater Plateau groundwater system. This aquifer is recharged by area streams where permeable basalts are exposed in stream channels (allowing for infiltration) and by precipitation percolating through fractured bedrock in the upland plateaus.

The Army Corp of Engineers (ACOE) defines wetlands as:

• areas where vegetation is predominately hydrophytic (i.e., adapted for life in saturated environments),
• areas where the presence of hydric soils or characteristics of reducing conditions persist, and saturated or inundated conditions exist permanently or periodically during the growing season (Corps of Engineer Wetlands Delineation Manual, 1987).

Based on the NRCS soil survey and the 1992 Natural Resource Inventory (conducted by NRCS) over 7,600 acres of wetlands were identified within the District. To determine the types of wetlands the USFWS draft Wetland Inventory maps were used.

The results of these inventories need additional detail to provide on-site classification. However, for general purposes these inventories will assist in identification of key areas and resource needs.

Predominate wetland types found in the District are Palustrine and Riverine systems. Lacustrine wetlands are also found in the District but these are less common and confined to large lakes or slack water areas created by the Lower Granite Dam.

Palustrine wetlands are defined as those wetlands with less than 20 acres, lacking wave formed or bedrock shoreline features, depth at low water less than two meters, and having a salinity content of less than 0.5%. Palustrine wetland systems consist of several vegetation types including trees, shrubs, emergent herbs and grasses, or emergent mosses and lichens. These areas may also lack vegetation. Depending on vegetation types Palustrine wetlands may be characterized as swamps, marshes, bogs, fens, wet meadows, etc. In Nez Perce County Palustrine wetlands are often associated with floodplains and are commonly found in croplands, range, and forested areas. Examples of this type of wetland in the District may include marshes, wet meadows, and swamps, but are not limited to these types.

Riverine wetlands are confined within the stream channel and are bordered by the stream bank or manmade levees, upland habitats, or by Palustrine wetlands. These wetlands are associated with free flowing water habitats in the District such as the Clearwater and Snake Rivers and their tributaries.

Lacustrine wetlands are associated with lakes or dammed river channels where the surface area greater than 20 acres. Shorelines are comprised of bedrock or formed by wave action. These wetland systems have less than 30% aerial cover of vegetation. Examples of this wetland type are present in the slack water areas of the Snake River created by dams, and within lakes or reservoirs such as Soldiers Meadows and Waha Lake.