![]() Similarly, putting t = 1 day, 1 month (30 days), 1 year (365 days), and 2 years (730 days), the specific capacities are computed as 273, 234.5, 212, and 207 1pm/m, respectively. What is the drawdown in the well after pumping for one year at the rate of 1200 1pm? Assume a well loss coefficient of 1950 sec 2/m 5. Construct specific capacity curves for the well for t = 1 hr, 1 day, 1 month, 1 year and 2 years of draught, when the well is pumped at the rate of- (a) 600 1pm, (b) 1200 1pm, and (c) 2000 1pm. The efficiency of a well, for a specified duration of pumping, is given by-Ī 30 cm well penetrates fully an infinite non-leaky artesian aquifer having T = 6.5 × 10 5 lpd/m, S = 0.0004. The percentage increase in discharge for the increase in diameter is given in Table 5.21 and illustrates the fallacy of the idea that big wells necessarily mean proportionately large yields. (5.5) and (5.7), Q is inversely proportional to log 10 R/r w. The maximum safe yield of a well or well field is the capacity of the aquifer to supply water without causing a continuous lowering of the water table or piezometric surface and is, therefore, limited by the rate at which the ground water is replenished by rainfall.Įxcessive lowering of the ground water table by pumping may result in crop failures, depletion of a nearby stream by increased percolation losses, salt water intrusion in coastal aquifers, and occasionally serious settlement of the ground surface.Īlso from Eqs. If the well is small in diameter and is pumped at a higher rate, the friction losses will increase. ![]() The probable drawdown for an unconfined aquifer may be obtained from Īnd for a confined aquifer Which shows that the specific capacity of a well is not constant but decreases with the increase in pumping rate (Q) and prolonged pumping (t) (Fig. This is a measure of the effectiveness of a well. ![]() ![]() The specific capacity (Q/s w) of a well is the discharge per unit drawdown in the well and is usually expressed in lpm/m. ![]()
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