Characterization of seasonal effects on the specific ...
Transcript of Characterization of seasonal effects on the specific ...
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. GierkeDepartment of Geological Eng. & Sciences
Michigan Technological University
Antoinette KomeSNV 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 Statement
• Practically no information 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
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.
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 GroupFractured 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
• Pump 60 – 90 gal
• Approximate rate of 5 gpm
Well 2 - 2/10/07
-0.5
0.0
0.5
0 20 40 60 80 100 120 140 160 180 200
Elapsed time (min)
of 5 gpm
• Allow well to recover for an hour or more
• Triplicate tests
-4.0
-3.5
-3.0
-2.5
-2.0
-1.5
-1.0
Dra
wd
ow
n (f
t)
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
Recuperation
Pumping
ExplanationWell 2: 1/11/07
-3.00
-2.00
-1.00
0.00
Dra
wd
ow
n (f
t)
Test 1 levelogger
Test 2 levelogger
Test 3 levelogger
Test 3 sounder
Equ
ilibr
ium
dr
awdo
wn
-6.00
-5.00
-4.00
-3.00
0 500 1000 1500 2000 2500 3000 3500
Elapsed Time (sec)
Dra
wd
ow
n (f
t)
Test 3 sounder
Test 2 sounder
Test 1 sounder
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’
SrTt
TsQ
2
3.0log264
=Cooper-Jacob Approximation in “Conventional” Units:
JSL: T=264 Q/ s JSL: T=264 Q/ s’
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 RAINY
��
��
�
�
�
�
��
�������� �������� ����� ����� ������ ������ ������ ��� �� �������
����
10/22/06 12/11/06 1/30/07 3/21/07 5/10/07 6/29/07 8/18/07 10/7/07 11/26/07
DRY RAINY
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
����
Specific Capacity Changes
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0Well 1
Well 2
Well 4
Specific capacity (attained from recovery data) vs. SWL
WellChange SWL (ft)
Change SWL (% available
water column)*
% Change Specific Capacity
1 6.6 4 % 15 %
2 4.4 2.5 % 26 %
3 6.3 3.5 % --
4 7.9 4.8 % 81 % *Assuming 200’ well
0.0
0.2
0.4
-1.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0
Feet below SWL Dec 06
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
Well 1
0.0
0.5
1.0
1.5
2.0
2.5
Non-equilibriumrecoverycurveEquilibriumapprox
Linear (Non-
Analysis method comparison
Well 2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
25.5 26.5 27.5 28.5 29.5 30.5 31.5
Equilibriumapprox
Non-equilibriummethod -recoverycurveNon-equilibriummethod -pump curve
Linear
Factorof 2
Factorof 2
36.0 38.0 40.0 42.0 44.0Static Water level (ft btc)
25.5 26.5 27.5 28.5 29.5 30.5 31.5
Static Water Level (ft btc)
Well 4
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
35 36 37 38 39 40 41 42 43 44
SWL (ft btc)
Equilibriumapprox
Non-equilibriummethod -recovery curve
Non-equilibriummethod - pumpcurve
Linear (Non-
Factorof 2
Spec. cap values calculated from :
equilibrium approx
recovery curve
pump curve
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
����
Well 4
2.0
2.5
3.0
3.5
4.0 Equilibriumapprox
Non-equilibriummethod -recovery curve
Non-equilibriummethod - pumpcurve
Spec. cap values calculated from manual tests:
equilibrium approx
recovery curve
pump curve
Conventional pump test comparison
0.0
0.5
1.0
1.5
2.0
35 36 37 38 39 40 41 42 43 44
SWL (ft btc)
curve
Trad Equilibriumapprox
Trad Non-equilibrium-pumpcurve
Trad Non-equilibrium-recovery curve
Spec. cap values calculated from conventional test:
equilibrium approx
recovery curve
pump curve
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
Conclusions (1 of 2)
On method:
� Manual test pump rate low, but results are representative of well behavior at high rates (in this case 7 times higher).
� Recovery data easiest to collect and yields � Recovery data easiest to collect and yields accurate specific capacity values.
�Overestimated specific capacity of wells as determined by equilibrium drawdown method maybe caused by lack of understanding of geology.
� Modifications to well for manual pump test minor, economical.
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
Conclusions (2 of 2)
On seasonal effects:
� Current water demands not affected by seasonal change in the static water level.level.
� Method determined that max capacity of wells to be at least 10X greater than what rope pump well delivers.
� Observed changes in productivity with even slight changes in SWL.
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
Thank You
Financial Support:• National Science Foundation PIRE 0530109• DeVlieg Foundation• SNV Nicaragua• U.S. Peace Corps
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, Beth Myre,
and the Families of 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