Rainwater harvesting and artificial groundwater recharge to improve

Kwemakame Spring Yields

Harry Rolf SamSamwater

27/10/2014

Project Location

• Tanga region• Lushoto district• Kwemakame / Kwai villages

Kwemakame project history• Chamavita, Kees Kempenaar • <1989 construction of gravity water scheme• 2004 ‘depletion’ • 2007 practical research project

– Cause of depletion?– How to improve?

• 2007 – 2010 field investigations &monitoring• 2010/2012 pilot design & construction• 2013 ‘post-pilot’ monitoring and reporting• 2014 dissemination

Project PartnersLocal Partners:• Village Kemakame/Kai

• Chamavita (Chama cha maendaleo vijijini tanga)

• Pangani Basin Water Office

The Netherlands:• AquaforAll (funding)• Aquanet (funding)• PWN/SamSamWater (techn.

Assistance)• SPOT Tanzania

Kwemakame/Kwai Estimated 3000 people

• Kwai/Kwemamake Water Board• 9 sub-villages

Water demand 1 liter/sec

Scheme constructed 1989, but the yield dropped since the initiation

Present Water sources (dry season):• Dindira ‘spring’ catchment (0,35 l/sec)• Kidandi ‘spring’catchment (0,15 l/sec)

Total yield Dindira

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

01/0

1/11

01/0

3/11

01/0

5/11

01/0

7/11

01/0

9/11

01/1

1/11

01/0

1/12

01/0

3/12

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5/12

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7/12

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9/12

01/1

1/12

01/0

1/13

01/0

3/13

disc

harg

e in

l/se

c

tot flow monthly avg

estimated demand (including animals)

domestic only

Study area

Water catchment is up in the mountains at Dindira

Dindira Valley 1950 – 2000 masl

Bedrock outcrop

Dindira shallow aquifer

Impervious base

2100 m

2000 m

1950 m

Gravity spring captation

Impervious base

Rainfall and evapotranspiration

Recharge

‘spring’ wall intake

Water intakes

Water scheme

From 11 intakes to 5 collection chambers

From collection chambers to main storage tank

From storage tank down to village distribution

Dindira main Storage tank 1850 m

Distribution area 1650 m

Water point Dindira hamlet

Research methodology

• Monitoring (Rainfall, evaporation, yields,…)• Field reconnaisance • Mapping• Analysis/ understanding

MonitoringRainfall & pan evaporation

Training

data collectors

Manual discharge reading in collection chambers

Groundwater levels

GPS mapping

Geo electrical sounding & profiling

Auger drilling

Water quality testing

AnalysisWenner profile Dindira (Kwemakame) intake nr.2 sub-catchment

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

-10 -7.5 -5 -2.5 0 2.5 7.5 10 12.5 17.5 20 22.5 27.5 30 32.5 37.5 40 42.5 47.5 50 52.5 57.5 60 62.5 67.5

distance from centre (m)

altit

ude

(m)

100

1000

1000

groundsurface (waypoints)ground surface (interpret)apparent res (Ωm) 3x5mapparent res (Ωm) 3x10m

outcrop

Aquifer properties

Cumulative rainfall

0

200

400

600

800

000

200

Nov Dec Jan Feb March April May June July August Sept Oct

Dindira 2007/2008Dindira 2008/2009Normal Rainfall (New LocClim)Normal rainfall LushotoDindira 2009/2010

Rainfall analysis

Kwemakame total discharge

0

10

20

30

40

50

60

jan/

08m

rt/08

mei

/08

jul/0

8se

p/08

nov/

08ja

n/09

mrt/

09m

ei/0

9ju

l/09

sep/

09no

v/09

jan/

10m

rt/10

mei

/10

jul/1

0se

p/10

rain

fall

(mm

/day

)

00.511.522.533.5

disc

harg

e (l/

sec)

rainfall (mm

flow in ch 5

27/10/06 chamber 5

Rainfall discharge relationship

Reasons for depletion

• Over decades: deforestation.• Rapid population increase• Climate change? (no proof)• Since 1989: using up groundwater storage

Generally:Too little recharge,while still rainwater is flowing out overland

Reasons for depletion (2)Using up groundwater storage

Too little recharge

Rain water is running off , being lost out of the area

Intakes are just ‘scraping off’ recharge

Groundwater dropping in the years after initiation

Key to improvement

INCREASE THE AMOUNT OF RAINWATER INFILTRATION

(‘Recharge enhancement’)

Strategy options

• Plant trees (yes, good solution on the long run)

• (Let it rain more)• (Pump water)• (Deeper intake wall)• (Surface water storage and treatment)• Add water in the underground:

– ‘artificial recharge’

Strategy to improve

Artificial Recharge:– Harvest rainwater that is running of– Temporary storage– Infiltration in the underground– ‘boost’ groundwater > increase yield

3R RetentionRechargeRe-use

Dindira Pilot to prove strategy

)

Existing intake nr 2

Infiltration pit

storage (hillside) dam

Pilot 1

Hillside dam location

Runoff catchment & diversion channel

Hillside dam

Infiltration pit

Filter trench and infiltration pit

SHIDA KUBWARain disaster April

2012Dam repaired and

re-enforced summer 2012

Fillings of the dam Dec 2012 – May 2013

0.0

0.3

1 Dec 12 21 Dec 12 10 Jan 13 30 Jan 13 19 Feb 13 11 Mar 13 31 Mar 13 20 Apr 13 10 May 13 30 May 13

wat

erle

vel r

eser

voir

(m)

0

10

20

30

40

50

60

prec

ipita

tion

(mm

/day

)

Precipitation (mm/day) Level (m+diver) Manual measurements

as recorded by diver logger and handreadings

Run off

Run off from bedrock

Water diversion to the dam

Fillings of the reservoir

Infiltration through the reservoir bottom

Release to the infiltration pit(after 1 day settling)

Results

A total amount of 2,5 million liters has been infiltrated

This water is added to groundwater and slowly flows down to intake, flowing out in the dry season

Some intakes were closed,conserving groundwater for the dry season. This has been beneficial as well.

2013 dry season effect:The people from Kwemakame/Kwai noticed considerably more water.

“we don’t know exactly what you’ve been doing up there in Dindira, but it helped a lot. We didn’t experience having so much water for many years. Even in the last dry months we had water all day long”.

Dry season yield monitoring

year month yield (l/sec)2009 Oktober 0.152010 November 0.422011 September 0.312012 November 0.25

average before the project: 0.302013 November 0.702014 29/10/2014 0.90

Observed yield of the Dindira Water Catchment at the end of the dry season

•Yield increased from 0.30 to 0.80 l/sec•Kwemakame/Kwai requires is 1.0 l/sec•Kidandi source gives 0.15• The required water is now available

CONCLUSIONS• Rainwater harvesting and infiltration by

artificial recharge can significantly improve the water supply

• Water conservation by closing intakes during the rain season adds a positive effect as well.

• Proper maintenance and operation is a first requirement for sustainability

• The community, Chamavita and Pangani Basin Water were deeply involved in this project and gained a lot of new knowledge on how to improve the ‘spring’ water catchment system. They are eager to replicate and upscale the concept to similar water schemes.

CHALLENGES AND LESSONS LEARNED• Assessment of runoff (where, how much)• Proper operation and maintenance is crucial • Re-use Silts that are trapped in the dam• Construction of earth dams on steep slopes.• To replicate this in other areas, you first need to

understand the groundwater system• For this understanding hydrological monitoring

is required (yields, groundwater levels, rainfall,…)

Other (technical) lessons learned.• It is extremely difficult to manage extensive hydrological

monitoring without experts on the ground, who are continuously analysing and checking the quality of the data collection.

• Know your runoff in the early project stages. It is important to know how much runoff water is there to catch. In our case the runoff was less than expected. Runoff tracks must be identified (and quantified) beforehand during heavy rains.

• Rainfall variability is high. For quantification purposes it is essential to have multiple rain stations over the catchment, measuring not only daily totals but rainfall intensity as well.

• The results show that rationing is effective, saving additional water for the dry season. In particular think of closing the highest intakes during the rain season ( starting with nr.2)

• How much and how fast will the infiltration water flow out at the source/intake: a set of ‘design rules’ is required.

• Proper operation and maintenance of the facility and its surroundings is required to assure that it will continue supplying.

Water quality• Indication of raised Nitrate contents by

agriculture • Water source protection must be addressed• Artificial recharge preferably in the forest area,

lakini….

Asante

MASWALI ?

The other pilot, pilot nr.2

new intake

storage

(valley) dam

Pilot 2 DESIGN

Pilot 2 area

Valley dam location

construction

Auger drilling

Auger drilling

New intake

Auger drilling

outlet pipe trench

• Unfortunately the new intake has much less water than expected

• Permanent Groundwater seepage flow to the dam 5000 lita every day!

• This water is treated by a SSF (Slow Sand Filter)

4000 l/day5000 l/day

• Very unfortunately the new intake has much less water than expected due to bad siting (by us).

• The aquifer is largely blocked by clays• In stead the water is seeping to the

reservoir (4000 l/day)• Water is treated by a Slow Sand Filter

Slow sand filter

MASWALI ?

Rainwater runoff