1. A Technologically Appropriate Method for Measuring the Specific Capacity of Rope-Pump Wells John S. Gierke 1, Essa L. Gross 1 & Elizabeth A. Myre 2 1 Department of Geological & Mining Engineering & Sciences 2 Department of Civil & Environmental Engineering Michigan 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  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? 60’

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. Santa Rita Study Area

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

8. Hydrogeology 200’ 50’ 160’ 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

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. After Gross (2007)

12. Straight-Line & Equilibrium Drawdown Methods

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

14. Seasonal Changes in Specific Capacity Well SWL Change (ft) SWL Change (% available water column)* % Change Specific Capacity 1- 6.6- 4.0 %- 15 % 2- 4.4- 2.5 %- 26 % 3- 6.3- 3.5 %-- 4- 7.9- 4.8 %- 81 % *Assuming 200’ well Drop in SWL (ft) from Dec 2006 Specific Capacity (gpm/ft)

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

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

18. Comparison of Data Analysis Methods Method Accounts for casing storage? T (gpd/ft) JSL (pumping) no296 GMS-MODFLOW Calibration (pumping) yes364 P-C AQTESOLV (pumping) yes367 JSL (late recovery) no438 GMS-MODFLOW Calibration (pumping and recovery, 1) yes528 Equilibrium Drawdown (equilibrium) n/a593 P-C AQTESOLV (pumping and recovery) yes630 GMS-MODFLOW Calibration (pumping and recovery, 2) yes653

19. Conclusions: Method 3.Recovery data easiest to collect and yields representative well behavior, equilibrium behavior easier to analyze 4.Modifications of wells for manual pump test are minor & economical 1.Wells are currently used at 1/10 th of their maximum capacity 2.Although the manual pump rate is low, results are representative of well behavior at high rates, at least 7X higher

20. Conclusions: Seasonal Effects 2.Current water demand places a negligible stress on the aquifer compared to seasonal changes in the static water level 3.Systematic monitoring is needed for management 1.Changes in specific capacity were observed for even slight changes (~ foot) in SWL

21. 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