Characterization of seasonal effects on the specific capacity of rope-pump wells in a fractured rock-aquifer in Nicaragua Essa L. Gross and John S. Gierke Department of Geological Eng. & Sciences Michigan Technological University Antoinette Kome SNV Nicaragua E.L.Gross, "Characterization of seasonal effects on the specific capacity of rope-pump wells in a fractured rock-aquifer in Nicaragua” AWRA conference, Alb, NM 2007
Outline � Problem Statement � Research Objectives � Study Area � Study Area � Methodology � Results � Conclusions E.L.Gross, "Characterization of seasonal effects on the specific capacity of rope-pump wells in a fractured rock-aquifer in Nicaragua” AWRA conference, Alb, NM 2007
Problem Practically no information • Statement exists on the productivity of rural wells in developing countries. Policy makers have no • information to base decisions or to develop water management plans. water management plans. The lack of technical and • economic resources prevents the collection of performance and monitoring data. E.L.Gross, "Characterization of seasonal effects on the specific capacity of rope-pump wells in a fractured rock- aquifer in Nicaragua” AWRA conference, Alb, NM 2007
Research Objectives Design and test a method to characterize the productivity of existing rope-pump wells in rural areas of developing countries Monitor seasonal changes in SWLs and specific capacities of rope-pump wells in an area that experiences distinct rainy and dry seasons. E.L.Gross, "Characterization of seasonal effects on the specific capacity of rope-pump wells in a fractured rock-aquifer in Nicaragua” AWRA conference, Alb, NM 2007
Outline � Problem Statement � Research Objectives � Study Area � Study Area � Methodology � Results � Conclusions E.L.Gross, "Characterization of seasonal effects on the specific capacity of rope-pump wells in a fractured rock- aquifer in Nicaragua” AWRA
Study Area Santa Rita E.L.Gross, "Characterization of seasonal effects on the specific capacity of rope-pump wells in a fractured rock- aquifer in Nicaragua” AWRA conference, Alb, NM 2007
Regional Geology � � � � � � � � � � � � � � � � � � � � � � � � Tpc - Coyol Group Fractured ignimbrites, tuff, andesite, basalt Source: INETER E.L.Gross, "Characterization of seasonal effects on the specific capacity of rope-pump wells in a fractured rock-aquifer in Nicaragua” AWRA conference, Alb, NM 2007
Rope-pump well 60’ E.L.Gross, "Characterization of seasonal effects on the specific capacity of rope-pump wells in a fractured rock-aquifer in Nicaragua” AWRA conference, Alb, NM 2007
Outline � Problem Statement � Research Objectives � Study Area � Study Area � Methodology � Results � Conclusions E.L.Gross, "Characterization of seasonal effects on the specific capacity of rope-pump wells in a fractured rock-aquifer in Nicaragua” AWRA conference, Alb, NM 2007
Testing and Monitoring Approaches Monthly manual pump tests in triplicate at 3 wells • Each test conducted to attain pumping, equilibrium, and recovery • phases A conventional step-drawdown test performed in one well • E.L.Gross, "Characterization of seasonal effects on the specific capacity of rope-pump wells in a fractured rock-aquifer in Nicaragua” AWRA conference, Alb, NM 2007
Pump test regime Well 2 - 2/10/07 Elapsed time (min) 0.5 • Pump 60 – 90 gal 0.0 0 20 40 60 80 100 120 140 160 180 200 • Approximate rate -0.5 of 5 gpm of 5 gpm -1.0 Drawdown (ft) • Allow well to -1.5 recover for an hour -2.0 or more -2.5 -3.0 • Triplicate tests -3.5 -4.0 E.L.Gross, "Characterization of seasonal effects on the specific capacity of rope-pump wells in a fractured rock-aquifer in Nicaragua” AWRA conference, Alb, NM 2007
Explanation Well 2: 1/11/07 0.00 -1.00 Pumping Test 1 levelogger down (ft) -2.00 Test 2 levelogger Recuperation Test 3 levelogger Drawdow Test 3 sounder Test 3 sounder -3.00 -3.00 Test 2 sounder Test 1 sounder -4.00 Equilibrium drawdown -5.00 -6.00 0 500 1000 1500 2000 2500 3000 3500 Elapsed Time (sec) E.L.Gross, "Characterization of seasonal effects on the specific capacity of rope-pump wells in a fractured rock-aquifer in Nicaragua” AWRA conference, Alb, NM 2007
Equilibrium drawdown Data analysis method E.L.Gross, "Characterization of seasonal effects on the specific capacity of rope-pump wells in a fractured rock-aquifer in Nicaragua” AWRA conference, Alb, NM 2007
Pump and recovery curves Data analysis methods Log Log s s’ JSL: T=264 Q/ s JSL: T=264 Q/ s’ Q T = Cooper-Jacob Approximation in Tt s 0 . 3 “Conventional” Units: 264 log r S 2 E.L.Gross, "Characterization of seasonal effects on the specific capacity of rope-pump wells in a fractured rock-aquifer in Nicaragua” AWRA conference, Alb, NM 2007
Outline � Problem Statement � Research Objectives � Study Area � Study Area � Methodology � Results � Conclusions E.L.Gross, "Characterization of seasonal effects on the specific capacity of rope-pump wells in a fractured rock-aquifer in Nicaragua” AWRA conference, Alb, NM 2007
Change in static water level ��������������������������������������� � ������ � Average dry season drop = 6 ft ������ ������ �� ������ �� DRY DRY RAINY RAINY �� ���� �� �� �� �� �� �� E.L.Gross, "Characterization of seasonal effects on the specific capacity of rope-pump �������� �������� ������� ������� ������� ������� ������� ������� �������� 12/11/06 1/30/07 3/21/07 5/10/07 6/29/07 8/18/07 10/7/07 11/26/07 10/22/06 wells in a fractured rock-aquifer in Nicaragua” AWRA conference, Alb, NM 2007 ����
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Specific Capacity Changes Specific capacity (attained from recovery data) vs. SWL 2.0 Well 1 1.8 Well 2 1.6 Well 4 1.4 1.2 1.0 0.8 0.6 0.4 0.4 0.2 0.0 -1.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 Change SWL % Feet below SWL Dec 06 (% available Change Change water Specific Well SWL (ft) column)* Capacity 6.6 4 % 15 % 1 4.4 2.5 % 26 % 2 6.3 3.5 % -- 3 E.L.Gross, "Characterization of seasonal effects on the specific capacity of rope-pump 7.9 4.8 % 81 % 4 wells in a fractured rock-aquifer in Nicaragua” AWRA conference, Alb, NM 2007 *Assuming 200’ well
Analysis method comparison Well 1 Well 2 2.5 1.4 1.2 2.0 Equilibrium 1.0 approx Factor Non- 1.5 0.8 equilibrium Factor Non- recovery of 2 equilibrium curve method - Equilibrium of 2 0.6 recovery 1.0 approx curve Non- 0.4 equilibrium Linear (Non- method - pump curve 0.5 0.2 Linear 0.0 0.0 25.5 25.5 26.5 26.5 27.5 27.5 28.5 28.5 29.5 29.5 30.5 30.5 31.5 31.5 36.0 38.0 40.0 42.0 44.0 Static Water Level (ft btc) Static Water level (ft btc) Well 4 Spec. cap values 4.0 3.5 calculated from : 3.0 equilibrium approx Factor Equilibrium 2.5 approx of 2 ���� 2.0 Non-equilibrium recovery curve method - recovery curve 1.5 Non-equilibrium method - pump 1.0 curve pump curve Linear (Non- 0.5 0.0 35 36 37 38 39 40 41 42 43 44 E.L.Gross, "Characterization of seasonal effects on the specific capacity of rope-pump SWL (ft btc) wells in a fractured rock-aquifer in Nicaragua” AWRA conference, Alb, NM 2007
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Conventional pump test comparison Well 4 Spec. cap values calculated from manual tests: 4.0 Equilibrium approx equilibrium approx 3.5 Non-equilibrium recovery curve 3.0 method - recovery curve pump curve 2.5 Non-equilibrium method - pump curve curve 2.0 2.0 Trad Equilibrium Spec. cap values approx 1.5 calculated from conventional test: Trad Non- 1.0 equilibrium-pump curve equilibrium approx 0.5 Trad Non- equilibrium- recovery curve 0.0 recovery curve pump curve 35 36 37 38 39 40 41 42 43 44 SWL (ft btc) E.L.Gross, "Characterization of seasonal effects on the specific capacity of rope-pump wells in a fractured rock-aquifer in Nicaragua” AWRA conference, Alb, NM 2007
Outline � Problem Statement � Research Objectives � Study Area � Study Area � Methodology � Results � Conclusions E.L.Gross, "Characterization of seasonal effects on the specific capacity of rope-pump wells in a fractured rock-aquifer in Nicaragua” AWRA conference, Alb, NM 2007
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