Growth of the Reno/Sparks metropolitan area has resulted in development of rural and undeveloped land in the nearby Tracy Segment Hydrographic Area. A study of hydrology, inorganic water chemistry, distribution and movement of ground water, and water budgets for the 285 square mile hydrographic area began in 2000. Streamflow from the Truckee River and precipitation are dominant inflows of water to the Tracy Segment, and combined streamflow from the river and the Truckee Canal, along with evapotranspiration and consumptive water-use are the primary outflows. Estimated long term (1971–2000) mean-annual precipitation ranges in the study area from 150,000 to 200,000 acre-feet per year and during this study (water years 1998–2002) the range was adjusted from 130,000 to 174,000 acre-feet per year. Water year used herein is the 12-month period October 1 through September 30. The water year is designated by the calendar year in which the 12-month period ends. Data from two micrometeorological stations located at 5,000 and 6,000 feet above sea level indicated that evapotranspiration of surface and soil moisture consumed 124,000 to 158,000 acre-feet per year during water year 2002. An additional 6,000 acre-feet per year is estimated to be transpired from ground water by phreatophytes