Laserfiche WebLink
Net recharge is that portion of infiltrating precipitation and surface water that actually contributes <br /> to increasing groundwater storage. Most recharge to groundwater occurs during the spring <br /> snowmelt period when evaporation and evapotranspiration is low. Existing topographic and <br /> hydrologic data indicates that net recharge tends to occur in the headwaters of the watershed, in <br /> the valley slopes bordering Little Turkey Creek, and east of the West Fault. In these areas, the <br /> groundwater table (saturated groundwater condition) is below the ground surface or the surface <br /> water elevation. <br /> The CGFM assumes that discharge from the groundwater system occurs in the form of seeps and <br /> springs, diffuse discharge to creek surface flows, evaporation/evapotranspiration, and pumpage <br /> from wells. Evaporation and evapotranspiration is accounted for in the water balance approach <br /> by using the concept of"net" recharge, which is the difference between total recharge and the <br /> sum of evaporation and evapotranspiration. <br /> Groundwater discharge from domestic wells in the Little Turkey Creek watershed is fairly <br /> limited. There are about a dozen operating domestic wells completed in the fractured <br /> granodiorite west of the HRR property, and all are relatively low yielding (typically <5gpm). <br /> Domestic wells completed in the sandstones of the Fountain Formation, east of the fault zone, <br /> have slightly higher yields but still account for a very small percentage of total groundwater <br /> discharge. <br /> Groundwater discharge, via seeps and springs or diffuse discharge to creek surface water flows, <br /> occurs in areas where the groundwater potentiometric head elevation is above the ground surface <br /> or the surface water elevation. Existing topographic and hydrologic data indicates that <br /> groundwater discharge tends to occur in the areas close to the Little Turkey Creek channel along <br /> the lower elevation reaches west of the West Fault. In these areas, the groundwater table <br /> (saturated groundwater condition) is at or above the ground surface or the surface water elevation. <br /> A numerical flow model was developed for the Little Turkey Creek watershed and used as a <br /> water balance tool to perform the evaluation. The MODFLOW computer code10 was used as this <br /> is an industry standard for numerical flow modeling. MODFLOW is the U.S. Geological Survey <br /> modular finite-difference flow model, which is a computer code that solves the groundwater flow <br /> equation. The program is used by hydrogeologists to simulate the flow of groundwater. The <br /> source code is free public domain software", written primarily in Fortran, and can compile and <br /> run on Microsoft Windows or Unix-like operating systems. <br /> to McDonald, M.G. & Harbaugh, A.W. (December 28, 1983). A modular three-dimensional finite- <br /> difference ground-water flow model. Open-File Report 83-875. U.S. Geological Survey <br /> 11 Harbaugh, A.W., Banta, E.R., Hill, M.C., and McDonald, M.G. (2000). MODFLOW-2000, the U.S. <br /> Geological Survey modular ground-water model—User guide to modularization concepts and the Ground- <br /> Water Flow Process (PDF). Open-File Report 00-92. U.S. Geological Survey. <br /> TRANSIT MIX-HITCH RACK RANCH <br /> HYDROGEOLOGY AND IMPACT ANALYSIS <br /> E-3 <br />