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1). This would be analogous to the task of other Federal statistical programs that produce <br />and regularly update indicator variables that describe economic, demographic, and health <br />conditions of the Nation. Data sets and analyses produced by the assessment will be <br />posted on the Internet and published in reports and scientific journals. <br />Table 1. Summary of proposed indicators of water availability <br />Surface -water indicators <br />Streamflow: annual and periodic (S- to 10 year) summaries of average <br />annual flows, seasonal flows and low flows; and assessments of long -term <br />trends in these values <br />Reservoir storage, construction, sedimentation, and removal <br />Storage in large lakes, perennial snowfields, and glaciers <br />Ground -water indicators <br />Ground -water -level indices for a range of hydrogeologic environments and <br />land -use settings <br />Changes in ground -water storage due to withdrawals, saltwater intrusion, mine <br />dewatering, and land drainage <br />Number and capacity of supply wells <br />Number of artificial recharge facilities and volume of water recharged <br />Water -use indicators <br />Total withdrawals by source (surface water and groundwater) and sector (public <br />supply, domestic, commercial, irrigation, livestock, industrial, mining, and <br />thermoelectric power) <br />Reclaimed wastewater <br />Conveyance losses <br />Consumptive uses <br />Surface Water <br />Indicators of surface -water availability will include measures of both streamflow and surface - <br />water storage, each of which change continuously in response to natural and human - induced <br />processes. A goal of the assessment will be to report indicators of surface -water availability at <br />the scale of the 352 river -basin hydrologic accounting units. These accounting units are <br />watersheds that are typically from 5,000 to 20,000 square miles. <br />The surface -water indicators will include annual summaries, periodic summaries of changes <br />over 5 -year periods, and periodic assessments of longer -term trends. The annual summaries <br />will provide simple and concise representations of the net effects of climatic events, water <br />management, and water withdrawals on surface -water supply during a year, as well as from <br />one year to the next. The periodic summaries at 5 -year periods will be useful to evaluate <br />7 <br />