Orange County NC Website
Browse       Search
31 <br /> ea*&WCes <br /> SSURGO database' supplied with the SWAT model as assigned to areas defined by the NRCS soil series <br /> units' that cover the model area. Vegetative cover used to compute ET within the SWAT model was <br /> defined by the USGS land cover database'. <br /> Climatic data for the SWAT model was used for the 4 km x 4 km grid cell of the national PRISM <br /> database10 centered on the property and comprised daily values of precipitation, and minimum and <br /> maximum daily temperature for the 42 year period from January 1, 1982, to December 31, 2023. Figure <br /> 6 shows the distribution of annual precipitation and groundwater recharge computed with the SWAT <br /> model. Mean annual precipitation is 47.06 inches and mean annual recharge is 12.06 inches. Figure 6 <br /> shows the annual distribution of recharge and the values for 1983 through 2023. <br /> 100% 25 <br /> 90% • • <br /> • SWAT Recharge • <br /> 80% 20 <br /> —Normal <br /> 704 Distribution w <br /> m <br /> 60% - 15 <br /> X <br /> z 60% lap <br /> m <br /> m 40% 10 <br /> CC <br /> s 30% <br /> • c <br /> a 20% ¢ 5 <br /> a <br /> o- 10% <br /> • <br /> 0% ° ta <br /> 0 6 10 15 20 25 1982 1987 1992 1997 2002 2007 2012 2017 2022 <br /> Annual Recharge Inches <br /> Figure 6.--Annual distribution and annual recharge computed with the SWAT model. <br /> The steady state watertable elevations shown in Figure 5 were computed using the mean annual recharge. <br /> To assess the values of hydraulic conductivity used for the model it was run with both wells pumping at <br /> an average of 25 gallons/minute. This assessment required a slight reduction of the hydraulic conductivity <br /> of the bedrock to 0.25 ft/day from the initial estimated value of 0.33 in Table 3 to reasonably reproduce <br /> the reported drawdowns in the wells when pumping. Figure 7 shows the computed steady state water <br /> drawdown with both wells pumping. The average of the modeled drawdown in the wells is 87 feet which <br /> is close to the reported values shown in Table 3 of 90 feet <br /> 7 https://www.nres.usda.gov/resources/data-and-reports/soil-survey_geographic-database-ssurgo <br /> s https://websoilsurvey.nres.usda.gov/app/WebSoilSurvey.aspx <br /> 9 htt2s://www.usgs.gov/node/279743 <br /> 10 https://prism.oregonstate.edu/ <br /> 6 <br />