IWMI’s Yoshiaki Inadi takes a closer look at Sri Lanka’s water storage reservoirs, locally known as “tanks”, and the growing importance of “agro-wells” for accessing groundwater.
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A water-secure world
Today’s presentation
1.Review the past tank cascade system and ground
water recharge studies in IWMI
2. Agro-well development due to high ground water
level
3. Multiple benefits of high ground water level derived
from irrigation project
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Climate and cultivation season
• Climate seasons
• First inter monsoon – March to April
• Southwest monsoon – May to September
• Second inter monsoon – October to November
• Northeast monsoon – December to February
• Cultivation Season
• Yala: March to September – less rain in dry zone area
• Maha: October to February – major rainy season in dry zone area
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Water Balance and Groundwater
Studies in Tank Cascade
• Tank balance model in Thirappane Cascade System (TCS)
• Itakura 1995
• Shinogi 1997
• Shanthi 2002
• Sub-watershed balance (on going) – 2013 Ministry of Water Resource
Management/Water Resource Board of Sri Lanka
• JIRCAS conducting a utilization of water balance model study in
Thirappane (on going)
• Cascade study – upper Yan Oya - Matsuno -1996
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Thirappane Cascade
Located at Anuradhapra
district in the North Central
province
6 interlinked small tanks
are situated 8 km between
top and bottom tanks
Jun Itakura’s initiated Study
in 1991
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Economic benefits on recharging
ground water(home-garden produce)
Total value of US$14.4 million/year (Molle, F; Renwick, M
2005)
13,000 ha (satellite images)
Amount(sampling survey)
Value(local market price)
Fruit value US$8 million/year
Timber value of US$6.40 million/year
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Economic benefits on recharging
ground water(domestic water supply)
• value of drinking water is estimated at US$0.14 million/
year. (Molle, F; Renwick, M 2005)
average water supply cost of 15 Rs/m3 (recent
communal water supply projects)
average current usage of 20 liter/person/day and
population estimate of 120,000 (Irrigation Department)