Contents Habitat Science Home Forest & Fish Section Water Resources Section SSHIAP WDFW Habitat Home RELATED LINKS Washington State Department of Ecology's Web Site on instream flows   For more information on habitat issues, please contact the WDFW Habitat Program. habitatprogram@dfw.wa.gov Phone: 360-902-2534

Mitigation for Water Withdrawal Introduction Growth happens … At least two impacts are of concern for impacts to freshwater ecosystems: Growth requires water, and Growth occurs on the landscape of a watershed, affecting hydrological, geomorphological, and ecological processes. Residential and industrial growth results in impermeable surfaces that alter hydrology, yielding flashy high flows and reduced low flows. Riparian habitat is modified, impacting lateral connectivity and water quality. Mitigation Goals Retain or restore watershed functions and processes that maintain aquatic habitats. Key functions and processes include: Hydrology – timing and quantity and quality of water Connectivity Sedimentation Erosion Large woody debris recruitment Thermal flux Mitigation Strategies Control land use in headwaters and riparian areas. Headwater land area is where precipitation hits surface and enters soil. Headwater interception determines quality, quantity and timing of flow through the remainder of the stream. Maintaining natural vegetation, topography, and degree of soil disturbance and compaction will retain rates of water movement to stream headwaters. Riparian vegetation, together with hydrology and hydraulic conditions, controls rates of bank erosion and sedimentation. It determines the rate of woody debris input and the type and amount of other terrestrial organic input, including insects. Eliminate or reduce longitudinal barriers to maintain or restore longitudinal connectivity. Eliminate or reduce lateral barriers to restore lateral connectivity. Stream interactions with floodplain are key to stream function and restore or maintain rates of processes such as erosion and sedimentation. Implementation Get a seat at the table. Being effective means getting others to give you authority so that your opinions carry weight. Find allies. Who has goals that are at least partly consistent with yours? Embrace the common interests. Discard traditional animosities. Public water supply utilities have some common interests:   Clean water   Abundant water Flood control interest also have some common interests:   Flood height reduction Techniques Headwater land protection – Mitigate for every acre-foot annual withdrawal with protection (purchase/conservation easement/dedication) of 2 acre-foot equivalents. Where annual headwater precipitation is 36 inches, this would require protection of >2/3 acre, depending on rates of evapotranspiration and other causes of water loss. Calculations are standard for hydrologists. Doubling acreage mitigates for some of loss of lower basin land function due to development as well as direct flow loss. Riparian land protection – Mitigate for every acre-foot annual withdrawal with 2 acres of riparian protection, where width from stream bank includes whole floodplain width, including old or secondary channels. Artificial barrier (lateral or longitudinal) removal – Removal or setback of dikes contributes to more natural interaction of the stream and its watershed. Removal or reduction of dams or other artificial stream blockage restores movement of organisms and nutrients through the watershed. Stream shading – Riparian trees provide shade to keep water temperatures cooler. They also provide bank stability, cover in the form of roots, eventual input of large woody debris, and ongoing source of insects as food for fish. Establishing riparian trees can be useful mitigation, but determining an appropriate amount of tree establishment can be difficult. Successful establishment will require a number of years of effort and monitoring and response to monitoring. Pump-and-dump – Recharging streams from groundwater is a popular mitigation strategy whose efficacy remains to be clearly demonstrated. It may have merit, but it modifies natural processes and benefits need to be shown. Sixteen Mile Creek and Mill Creek confluence, Milton, Ontario. Photo by Lorne Fitch, Alberta Sustainable Resource Development, Fish and Wildlife Division – from IFC 2004 (Instream Flows for Riverine Resource Stewardship), Fig. 1-5c. Summary It’s not just the water in the stream. It’s how the water interacts with its watershed and channel. Successful protection of fish and wildlife habitat requires a broad view and taking advantage of any option that is available. Water in a concrete channel has minimal habitat value. Habitat is a product of climate, watershed, banks, channel, and water. Contact Hal BeecherWashington Department of Fish and Wildlife Phone: (360) 902-2421E-mail: beechhab@dfw.wa.gov Asotin Creek in SE corner of Washington has headwaters in Umatilla National Forest and flows into Snake River.