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 Engineering

Michigan Technological University

Antoinette Kome

SNV Nicaragua

Outline

Introduction &

Objectives

Methodology

Results & Conclusions

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

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’

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.

Santa Rita

Study Area

Regional Geology

Tpc - Coyol Group

Fractured ignimbrites,

tuff, andesite, basalt

X XXX

Source: INETER

HydrogeologyNo de Pozo: 126/02/02

Coordenadas: L. Nort L.Oest

200 pies 60.96 m

50 pies 15.24 m

160 pies 48.768 m

5 gpm 1.1354 m3/h

50 pies 15.24 m

18 gal. 68.13 litros

46 gal. 174.11 litros

8 gal. 30.28 litros

gal. 0 litros

8 gal. 30.28 litros

gal. 0 litros

80 gal. 302.8 litros

EMPRESA NICARAGUENSE DE ACUEDUCTOS RURALES Y ALCANTARILLADOSGerencia de Acueductos Rurales

REGISTRO DE POZOS

REVESTIMIENTO PERFIL GEOLOGICO DATOS GENERALESDepartamento: Chontales

Municipio: Juigalpa

Comunidad: Santa Rita

Elevacion (msnm):

0'-20' Basalto erocionado Gris(GR) Perforador: Carlos Largaespada

Supervisor-Geologo: Luis Meza Hurtado

20'-30 Basalto Compacto Fecha de inicio: 2/14/06

Fecha de finalizacion: 2/15/06

30'-60' Toba Calcitica (Mr) Metodo(s): Rotativo

Diametro(s) de perforacion: 77/8" y 51/4"

No de barras: 20

60'-90' Basalto (GR) Profundidad total:

NEA:

NFA:

90'-100' Toba Aglomeratica (MR) Caudal:

Metodo de bombeo:

Tiempo de bombeo: horas

100'-150' Basalto con pigmentaciòn cristalinaProfundidad del agua al final del bombeo:

DISTRIBUCCION DEL TIEMPO

Total de horas trabajadas 18:19

Tiempo de perforacion 6:57

150'-160' Basalto Fracturado Total de Tiempo muerto: 1:34

Causas del tiempo muerto:

Lluvias

160'-200' Basalto (Gr) con presencia de cristalReparacion y mantenimiento 0:34

Falta de materiales

Fuerza mayor

Falta de acceso

Problemas de perforacion

Alimentacion 1:00

Desarrollo 1:45

Otras actividades 8:03

CONSUMO DE DIESEL

Sonda de perforacion

Compresor

Camion Portasonda

Camion del compresor

Camioneta de apoyo

Camioneta supervision

TOTAL

NOTAS:

La perforac—n se desarrollo sin ningn problema, los tubos que se usaron para el encamisado del pozo, fueron de los que se sacaron en la salida de Apompua El Portillo, para el mismo se utilizaron un total de 22 tubos de 4" x 3 Mtrs.

No de Pozo: 126/02/02

Coordenadas: L. Nort L.Oest

200 pies 60.96 m

50 pies 15.24 m

160 pies 48.768 m

5 gpm 1.1354 m3/h

50 pies 15.24 m

18 gal. 68.13 litros

46 gal. 174.11 litros

8 gal. 30.28 litros

gal. 0 litros

8 gal. 30.28 litros

gal. 0 litros

80 gal. 302.8 litros

EMPRESA NICARAGUENSE DE ACUEDUCTOS RURALES Y ALCANTARILLADOSGerencia de Acueductos Rurales

REGISTRO DE POZOS

REVESTIMIENTO PERFIL GEOLOGICO DATOS GENERALESDepartamento: Chontales

Municipio: Juigalpa

Comunidad: Santa Rita

Elevacion (msnm):

0'-20' Basalto erocionado Gris(GR) Perforador: Carlos Largaespada

Supervisor-Geologo: Luis Meza Hurtado

20'-30 Basalto Compacto Fecha de inicio: 2/14/06

Fecha de finalizacion: 2/15/06

30'-60' Toba Calcitica (Mr) Metodo(s): Rotativo

Diametro(s) de perforacion: 77/8" y 51/4"

No de barras: 20

60'-90' Basalto (GR) Profundidad total:

NEA:

NFA:

90'-100' Toba Aglomeratica (MR) Caudal:

Metodo de bombeo:

Tiempo de bombeo: horas

100'-150' Basalto con pigmentaciòn cristalinaProfundidad del agua al final del bombeo:

DISTRIBUCCION DEL TIEMPO

Total de horas trabajadas 18:19

Tiempo de perforacion 6:57

150'-160' Basalto Fracturado Total de Tiempo muerto: 1:34

Causas del tiempo muerto:

Lluvias

160'-200' Basalto (Gr) con presencia de cristalReparacion y mantenimiento 0:34

Falta de materiales

Fuerza mayor

Falta de acceso

Problemas de perforacion

Alimentacion 1:00

Desarrollo 1:45

Otras actividades 8:03

CONSUMO DE DIESEL

Sonda de perforacion

Compresor

Camion Portasonda

Camion del compresor

Camioneta de apoyo

Camioneta supervision

TOTAL

NOTAS:

La perforac—n se desarrollo sin ningn problema, los tubos que se usaron para el encamisado del pozo, fueron de los que se sacaron en la salida de Apompua El Portillo, para el mismo se utilizaron un total de 22 tubos de 4" x 3 Mtrs.

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

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

Manual Pumping Test Regime

• Pump 60 – 90 gal

• Approximate rate of 5 gpm

• Well allowed to recover for at least an hour

• Triplicate tests

After Gross (2007)

Straight-Line & Equilibrium Drawdown Methods

Seasonal Change in SWLs

Average dry season drop = 6 ftAverage dry season drop = 6 ft

DRY RAINY

Sta

tic W

ater

Lev

el

(ft

bgs)

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

Spe

cific

Cap

acity

(gp

m/f

t)

Traditional pump test profile 9/25/07

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14 16 18 20 22 24 26

Elapsed time (hrs)

Dra

wd

ow

n (

ft b

tc)

5 gpm 15 gpm

25 gpm

37 gpm

Comparison of Pumping Test Methods

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)

Sp

ec

ific

ca

pa

cit

y (

gp

m/f

t)

Equilibriumapprox

Non-equilibriummethod -recovery curve

Non-equilibriummethod - pumpcurve

Trad Equilibriumapprox

Trad Non-equilibrium-pumpcurve

Trad Non-equilibrium-recovery curve

Linear (Non-equilibriummethod -recovery curve)Linear(Equilibriumapprox)

Linear (Non-equilibriummethod - pumpcurve)

Prueba perfil

-5.0

-4.5

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0 500 1000 1500 2000 2500

Prueba perfil

-5.0

-4.5

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0 500 1000 1500 2000 2500

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

Sp

ecif

ic C

apac

ity

(gp

m/f

t)

Curve Matching: Papadopolus-Cooper (1967) using AQTESOV

10-1

100

101

102

0.

1.6

3.2

4.8

6.4

8.

Time (min)

Dis

plac

emen

t (ft)

Obs. Wells

Church Well

Aquifer Model

Confined

Solution

Papadopulos-Cooper

Parameters

T = 366.9 gal/day/ftS = 0.2002r(w) = 0.177 ftr(c) = 0.177 ft

10-1

100

101

102

0.

1.6

3.2

4.8

6.4

8.

Time (min)

Dis

plac

emen

t (ft)

Obs. Wells

Church Well

Aquifer Model

Confined

Solution

Papadopulos-Cooper

Parameters

T = 629.6 gal/day/ftS = 0.01119r(w) = 0.177 ftr(c) = 0.177 ft

Comparison of Data Analysis Methods

MethodAccounts for

casing storage?T (gpd/ft)

JSL(pumping)

no 296

GMS-MODFLOW Calibration(pumping)

yes 364

P-C AQTESOLV(pumping)

yes 367

JSL (late recovery)

no 438

GMS-MODFLOW Calibration(pumping and recovery, 1)

yes 528

Equilibrium Drawdown(equilibrium)

n/a 593

P-C AQTESOLV(pumping and recovery)

yes 630

GMS-MODFLOW Calibration(pumping and recovery, 2)

yes 653

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 1/10th 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

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

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