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A Basin Study of Ground‐Water Discharge from Bedrock into Glacial Drift Part II–Estimate of Discharge
Author(s) -
Kent Douglas C.,
Sendlein Lyle V. A.
Publication year - 1972
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.1972.tb03587.x
Subject(s) - groundwater recharge , bedrock , aquifer , geology , hydrology (agriculture) , structural basin , groundwater , aquifer properties , geomorphology , geotechnical engineering
This is the second part of a two‐part series (Kent and Sendlein, 1972) in which an approximation of the quantity of bedrock recharge is made. Procedures used for the definition of the ground‐water system were described in Part I. In Part II, a subsurface ground‐water budget equates subsurface recharge from the bedrock aquifer to discharge through sand and gravel and to discharge by pumping. The Darcy equation is used to compute recharge and discharge volume flow rates. Estimates of permeability were obtained from existing pump‐test data and the hydraulic gradients were determined from the piezometric map. Two conceptual models are proposed to account for the maximum and minimum cross sectional areas of the bedrock aquifer through which ground water could flow into the sands and gravel and thus are used to represent the maximum and minimum limits of recharge. Upper, lower and average values of bedrock recharge are determined for each model and compared with the average natural discharge for the entire ground‐water basin (“total basin” approach). Comparisons are also made for portions of the basin (“partial basin” approach). Upper and lower limits of recharge are chosen from recharge values which are nearest to the average discharge estimate. This determination is based on the assumption that recharge is equal to discharge. Results of this study indicate a quantity of bedrock recharge between a lower limit of 0.23 mgpd and an upper limit of 2.5 mgpd is possible for an 800‐square mile basin. The purpose of this approach is to provide an approximation of ground‐water recharge from bedrock into an unconfined unconsolidated ground‐water basin, and to provide an estimate of its importance to urban ground‐water use.