Technique for estimation of streamflow statistics in mineral areas of interest in Afghanistan

Abstract

A technique for estimating streamflow statistics at ungaged stream sites in areas of mineral interest in Afghanistan using drainage-area-ratio relations of historical streamflow data was developed and is documented in this report. The technique can be used to estimate the following streamflow statistics at ungaged sites: (1) 7-day low flow with a 10-year recurrence interval, (2) 7-day low flow with a 2-year recurrence interval, (3) daily mean streamflow exceeded 90 percent of the time, (4) daily mean streamflow exceeded 80 percent of the time, (5) mean monthly streamflow for each month of the year, (6) mean annual streamflow, and (7) minimum monthly streamflow for each month of the year. Because they are based on limited historical data, the estimates of streamflow statistics at ungaged sites are considered preliminary. Introduction Afghanistan has many mineral areas of interest (fig. 1) that may be a source of economic opportunity for the country (Peters and others, 2007; 2011). Water is needed both for mining processes and to support the communities and related industries that may develop around a mining economy. Mining activities generally require large volumes of processing water, which may be obtained most economically from surface-water sources. Estimates of streamflow statistics are needed to assess whether sufficient water is likely to be available in local streams at various times of the year for both mining and community needs. Streamflow statistics, based on data collected from the mid-1940s to 1980, are available for 150 of 174 historical streamgaging sites in Afghanistan that were operated by the Afghanistan Ministry of Energy and Water (Olson and Williams-Sether, 2010; Williams-Sether, 2008; Vining, 2010). In some mineral areas of interest, however, no historical gages are present (fig. 1); therefore, methods for estimating streamflow characteristics in these areas are needed.