Low stream flow can block fish migration. In the Upper Chehalis watershed the combined allocation for surface water and ground water rights and claims totals 1,202 cfs per year. Applications are on file with Ecology for an additional 46 cfs. In winter when flows are high, additional water is available for allocation. However, in summer months, rights and claims exceed natural stream flow in many instances.
Irrigated agriculture accounts for the largest use of water in the watershed.
This use occurs during summer months when water is least available and most necessary for maintaining minimum base flows. Population growth is expected to increase steadily, requiring development of new water supplies. Sufficient water must be maintained in streams to adequately dilute permitted wastewater discharges. The environmental problems of water quality degradation and depletion of fish stocks, and the over-allocation of water rights have been identified in the Upper Chehalis watershed. Deny applications for new Water Rights unless acceptable mitigation is proposed.