2009 Annual Report 1a.Objectives (from AD-416) To quantify interactive effects of climate variability and land management on water availability and quality. 1b.Approach (from AD-416) The ARS Grazinglands Research Laboratory and Oklahoma State University are engaged in the measurement and analysis of weather, climate, and soil data. The Oklahoma Mesonet is a joint effort of the Divison of Agriculture Sciences and Natural Resources at Oklahoma State University in conjunction with the College of Geosciences at the University of Oklahoma for the purpose of maintaining a statewide network of automatic weather stations. 3.Progress Report Global climate change, decade-long and inter-annual climate variations, and changes in land use over large agricultural regions are believed to have a profound impact on regional water resources and water quality, thereby affecting urban and industrial water supply, hydro-electric power generation, transportation, recreation, and ecosystem sustainability. Only through a comprehensive monitoring program and hydrologic analysis of large watersheds can one identify management opportunities that positively impact downstream water availability and quality in terms of climatic conditions and land use change. Air temperature, relative humidity, solar radiation, and soil temperature (via thermistors) measurements were discontinued due to budget constraints. Soil temperature from the thermistors were replaced with those acquired from the soil moisture sensors. Under this subordinate project, precipitation and soil temperature at 20 sites on the Little Washita River Experimental Watershed and 15 sites on the Fort Cobb Reservoir Watershed were measured, quality controlled, and archived in collaboration with Oklahoma State University and in conjunction with the Oklahoma Mesonet, a network of climate stations covering the State of Oklahoma. ARS received and reviewed monthly reports on the status of instrument repairs and routine maintenance. An assessment was provided of instrumentation replacements or upgrades needed at the Micronet sites over the next 3 years to support ARS planning. Suspicious and erroneous data were flagged and instrument repairs were performed in a timely manner. The collected weather data are available to all ARS scientists, to the research community, and to the public in general, and are used to address research objectives outlined in the parent project. A public-accessible web page is supported where the real-time weather data can be viewed and downloaded. The ADODR monitored progress of the project through site visits, monthly quality control reports, e-mails, and telephone conversations.