What is aquifer step drawdown test?
Step drawdown test was conducted in this study as a part of aquifer test for various purposes. In this test the pumping rate is stepped up successively and drawdown for each step is recorded. The sum of the well loss and the aquifer loss is drawdown of the well.
What is step drawdown test?
SUMMARY A step drawdown test is a pumping test in which the drawdown in a well is observed while the discharge rate from the well is increased in steps. Step drawdown tests can be used to determine the aquifer transmissivity and the well loss component of the drawdown in the pumped well.
How do you calculate groundwater drawdown?
Subtract the measurements you collect as the pump is running from the static water level. The difference is the drawdown. For example, if the static water level is 1 foot below the top of the casing and the water level after one hour is 3 feet below the top of the casing, the drawdown at one hour of pumping is 2 feet.
What is a well drawdown test?
A well test is conducted to evaluate the amount of water that can be pumped from a particular water well. When water is pumped from a well the water level in the well falls. This fall is called drawdown. The amount of water that can be pumped is limited by the drawdown produced.
What is the purpose of step-drawdown test?
A step-drawdown test (or step test) is a single-well pumping test designed to investigate the performance of a pumping well under controlled variable discharge conditions.
How do you do a step-drawdown test?
In a step-drawdown test the well is initially pumped at a low constant rate until the drawdown within the well stabilises, i.e. until a steady state is reached. The pumping rate is then increased to a higher constant rate and the well is pumped until the drawdown stabilises once more (Figure 5.1).
How do you find the drawdown of an aquifer?
Drawdown s is the difference between the elevation of the piezometric surface prior to pumping Z(r,t=0) and the elevation of the piezometric surface during pumping Z(r,t>0). Thus: s(r,t) = Z(r,t=0) – Z(r,t>0).
What is drawdown in an aquifer?
Drawdown is a change in groundwater level due to an applied stress, caused by events such as: Pumping from a well. Pumping from a neighbouring well. Intensive water taking from local area. Seasonal declines as recharge rates lower.
What is drawdown in aquifer?
Drawdown is a term applied to the maximum lowering of the groundwater table caused by pumping or artesian flow (Figure D60). It is measured as the difference between the initial level of water in a well before pumping, and the static, or stabilized, level of water after a long period of pumping.
What is aquifer performance test?
An aquifer performance test is conducted to quantify the aquifer characteristics and estimate aquifer properties. like transmissivity and storativity. The presentation gives details of pumping test equipments and the mechanics of pumping (well hydraulics).
How do you calculate drawdown?
The investment drawdown is calculated by subtracting the maximum drawdown level from the high-water mark and dividing the difference by high-water mark. The largest percentage drawdown is used as the investment drawdown for an investment.
How do you predict a drawdown on a well?
Calculate the drawdown by subtracting the static level from the pumping level. saving well testing data. Also listed are some ways that you can use well drawdown measurements. Operating records should contain information about the static and pumping levels of a well, plus other important data.
When do you do a step drawdown test?
A step-drawdown test is a single-well test that is frequently conducted after well development to determine well efficiency and correctly size the production pump. Pumping rates are constant during steps which are of sufficient duration, about 1–4 hours, for water levels to change minimally at the end of each step ( Halford and Kuniansky, 2002 ).
How are water levels measured during a step drawdown?
Successively greater discharge rates are pumped during subsequent steps, where three to five discharge rates typically are tested. Water levels are measured prior to pumping, during each step, and during recovery so that drawdowns can be estimated.
How to calculate slope of a step drawdown?
Slope (T/L²) estimated from flow-normalized drawdown plot. T = 35.3 / Slope in field units of ft²/d, ft, and gpm. Discrete steps plot separately because of non-linear, well losses. Measured s/Qstep depart from straight lines at the beginning of each step because of wellbore storage.
How does the flow normalized drawdown plot work?
The flow-normalized drawdown plot also makes other departures between measured drawdowns and analytical model apparent such as the departure between measured and simulated slopes at highest pumping rate of 600 gpm (Figure 1, s/Qstep>0.7). Transmissivity of the aquifer likely was reduced by dewatering transmissive fractures.