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John S. Gierke 1 , Essa L. Gross 1 & Elizabeth A. Myre 2

A Technologically Appropriate Method for Measuring the S pecific C apacity of R ope- P ump W ells. John S. Gierke 1 , Essa L. Gross 1 & Elizabeth A. Myre 2

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John S. Gierke 1 , Essa L. Gross 1 & Elizabeth A. Myre 2

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  1. A Technologically Appropriate Method for Measuring the Specific Capacity of Rope-Pump Wells John S. Gierke1, Essa L. Gross1 & Elizabeth A. Myre2 1Department of Geological & Mining Engineering & Sciences2Department of Civil & Environmental EngineeringMichigan Technological University Antoinette Kome SNV Nicaragua

  2. Outline • Introduction & Objectives • Methodology • Results & Conclusions

  3. Introduction:Water Supply Issues for Developing Countries Practically no information exists on the capacity of rural wells Many areas suffer from lack of water during the dry season Management agencies have no information to develop water management plans Lack of technical and economic resources prevents the collection of performance and monitoring data

  4. Rope Pumps 60’ Originated in Nicaragua (1980s), has since proliferated there Usage outside of Nicaragua has been limited, can be driven manually or with wind Affordable and readily maintained Can they be adapted for using in pumping tests?

  5. Design and test a method to characterize the productivity of existing rope-pump wells in rural areas of developing countries Research Objectives Monitor seasonal changes in SWLs and specific capacities of rope-pump wells in an area that experiences distinct rainy and dry seasons.

  6. Study Area Santa Rita

  7. Regional Geology X X X X Tpc - Coyol Group Fractured ignimbrites, tuff, andesite, basalt Source: INETER

  8. Hydrogeology 0-20’ Weathered Basalt 20-30’ Compacted Basalt 30-60’ Tuff (cemented ash deposit) 60-90’ Basalt 90-100’ Tuff 100-150’ Basalt 150’-160’ Fractured basalt 160-200’ Basalt 50’ 160’ 200’

  9. Testing and Monitoring Approaches • Monthly manual pump tests in triplicate at 3 wells • Each test included pumping, equilibrium, and recovery phases • A conventional step-drawdown test performed in one well

  10. Manual Pumping Test Regime • Pump 60 – 90 gal • Approximate rate of 5 gpm • Well allowed to recover for at least an hour • Triplicate tests

  11. Pumping Test Phases After Gross (2007)

  12. Straight-Line & Equilibrium Drawdown Methods

  13. Seasonal Change in SWLs Average dry season drop = 6 ft DRY RAINY Static Water Level (ft bgs)

  14. Seasonal Changes in Specific Capacity Specific Capacity (gpm/ft) Drop in SWL (ft) from Dec 2006 *Assuming 200’ well

  15. Spec. cap values calculated from conventional test: equilibrium approx recovery curve pump curve Comparison of Pumping Test Methods Spec. cap values calculated from manual tests: equilibrium approx recovery curve pump curve Specific Capacity (gpm/ft)

  16. Curve Matching: Papadopolus-Cooper (1967) using AQTESOV

  17. Comparison of Data Analysis Methods

  18. Conclusions: Method • Wells are currently used at 1/10th of their maximum capacity • Although the manual pump rate is low, results are representative of well behavior at high rates, at least 7X higher Recovery data easiest to collect and yields representative well behavior, equilibrium behavior easier to analyze Modifications of wells for manual pump test are minor & economical

  19. Conclusions: Seasonal Effects Changes in specific capacity were observed for even slight changes (~ foot) in SWL Current water demand places a negligible stress on the aquifer compared to seasonal changes in the static water level Systematic monitoring is needed for management

  20. Acknowledgements We would like to acknowledge the following people for their assistance in this study: Gregg Bluth, Fernando Flores, Luis Meza, Denia Acuña, Evelio Lopez , Ivan Palacios, Elisena Medrano, Luis Palacios, and the Families of Santa Rita • Financial Support: • National Science Foundation PIRE 0530109 • DeVlieg Foundation • SNV Nicaragua • U.S. Peace Corps • MTU d80 Center & GMES Department

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