The Meheriin Watershed, also known as HUC 03010204, covers an area of 391 square miles in northeastern Oregon. The primary source of water in the watershed is snowpack, which typically accumulates from November to March and melts from April to June. The surface water flows into the Meheriin River and eventually into the Snake River. The Meheriin Watershed has several reservoirs that store water for irrigation, including the Unity Reservoir, which can hold up to 87,000 acre-feet of water. The reservoirs also contain several constituents, including nitrogen and phosphorus, which can lead to harmful algal blooms. The region experiences a semi-arid climate, with hot summers and cold winters. Climate models suggest that the region will experience more frequent and severe droughts in the future, which could further impact water availability and quality in the watershed.