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Pumping test

  2. What Is A Pumping Test? • A pumping test is a field experiment in which a well is pumped at a controlled rate and water-level response (drawdown) is measured in one or more surrounding observation wells and optionally in the pumped well (control well) itself; response data from pumping tests are used to estimate the hydraulic properties of aquifers, evaluate well performance and identify aquifer boundaries.
  3. Why we should performing Pumping Test • Principal part in many projects and studies dealing with groundwater exploitation, protection and remediation. • Aim to regulate and optimize the extraction without adversely impacting aquifer systems. • Pumping test gives the best information on the drawdown level, flow rates and unforeseen factors drawdown level, flow rates and unforeseen factors generated upon pumping.
  4. Principles of Pumping Test • Principles of Pumping Test involves applying a stress to an aquifer by extracting groundwater from a pumping well and measuring the aquifer response to that stress by monitoring drawdown as a function of time. • These measurements are then incorporated into an appropriate well- flow equation to calculate the hydraulic parameters of the aquifer. • It can be applied by Single-Well or Multi-Wells (observations)
  5. Pumping Test in Field
  6. Pumping tests are carried out to determine • How much groundwater can be extracted from a well based on long--term yield, and well efficiency. • The hydraulic properties of an aquifer or the hydraulic properties of an aquifers. • Spatial effects of pumping on the aquifer. • Determine the suitable depth of pump. • Information on water quality and its variability with time.
  7. Types of pumping tests • Constant-rate tests maintain pumping at the control well at a constant rate. This is the most commonly used pumping test method for obtaining estimates of aquifer properties. • Step-drawdown tests proceed through a sequence of constant-rate steps at the control well to determine well performance characteristics such as well loss and well efficiency. • Recovery tests use water-level (residual drawdown) measurements after the termination of pumping. Although often interpreted separately, a recovery test is an integral part of any pumping test.
  8. Stages involved in performing pumping tests • a) Preliminary studies • b) Estimation of Transmissivity Hydraulic conductivity • c) Selection of test site • d) Discharging well (i) Design and construction Well diameter Well depth Well screen length Gravel pack (ii) Selection of the pump (iii) Discharge of pumped water
  9. Cntd…. • e) Piezometer Number of piezometers Distance of piezometers Depth of piezometers • f) Performance of a pumping test (i) Measurements of the water level (ii) Measurements of discharge rate Analysis of data Compilation of the data
  10. Pumping Rate Measurement And Control • A controlled pumping stress is imposed on an aquifer system during a pumping test. Therefore, carefully measuring, controlling and recording the flow rate throughout the test is essential for a successful outcome. • Although a constant pumping rate is most often the goal, the rate may vary during a pumping test. Software such as AQTESOLV can account for variable pumping rates; however, results will depend on how closely the recorded flow rates correspond to actual rate changes.
  11. Water-Level Measurement • During a pumping test, water levels in wells may be measured by means of manual techniques or through the use of sensors with data loggers. • Manual Methods: Manual water-level measurement techniques include chalked stee tape, electric water-level sounders and air line methods.
  12. Cntd…. • Data Loggers: Pressure transducers combined with data loggers provide rapid and accurate measurements of water levels in wells.
  13. Duration of pumping test • It’s difficult to determine how many hours that pumping test required because period of pumping depends on the type and natural materials of the depends on the type and natural materials of the aquifer. • In general pumping test is still until pseudo--steady state flow is attained or low fluctuation in dynamic water is occur. • In some tests, steady state occurs a few hours after pumping, in others, they never occur. However,24--72 hours testing is enough to produce diagnostic data and to enable the remaining wells for testing. • Tests taking longer than 24 hours may be required for large takes, such as community supplies, or situations where it may take to determine effects.
  14. Disposal Of Pumped Water • Avoid direct discharge of water on the ground surface if the water is likely to recharge the pumped aquifer (e.g., a shallow unconfined aquifer or karst aquifer with sinkholes). Recycling of the pumped water through recharge can result in the false identification of a constant-head boundary or leakage. • Discharge of water to a surface water feature such as a stream is a viable option if it is anticipated that the surface water body is hydraulically disconnected from the pumped aquifer or if it behaves as a constant-head boundary. • Avoid adverse thermal, biological, water-quality, erosion or sediment mobilization impacts when discharging to groundwater or surface water and obtain appropriate discharge permits.