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HYDROLOGICAL DIAGNOSIS FOR INTEGRATED WATER MANAGEMENT

Congress: 2008
Author(s):

Keyword(s): Water availability, water use, water management
AbstractThe climate of the Earth is changing and that the impacts of climate change will be felt across national borders, ecosystems and the economic sector in the coming decades. According to IPCC, the globally averaged surface temperature is projected to increase by 1.4 to 5.8 deg 0C over the period 1990 to 2100. The air temperature over Sri Lanka has also been increasing particularly since 1960. In some parts of Sri Lanka, atmosphere is highly polluted. Aerosols such as industrial particulates has a higher value (109 g /m3) according to the Sri Lankan standard. Further concentrations of So2 (0.084ppm} and No2(0.073) exceeds Sri Lankan standards. Already unexpected flash floods, drought, ground water depletion are being experienced in the region. Therefore recommendations on adaptation strategies and mitigation options with regards to agriculture, water resources etc are need of the hour. To confirm the occurrence of dry spell of longer duration during the cultivation period, rain fall data of 30 year period from different locations were analyzed and found to fit Gamma distribution model [Y= 1/βα . T(α) . X (α -1) . e - (X/β) ] with coefficient of determination (R2 = 0.919001) showing a higher degree of predictability of expected values using the observed values. Pumping test carried out to study nature of the aquifers showed that the draw down period of the tested wells ranged from 10 to 140 minutes and time for the recharge of the wells ranged from 100 to 1200 minutes showing aquifers were not receiving adequate water for their recharge. Analysis of year to year variations of rice harvest showed that by and large during the EL-Nino climatic episodes, the Yala ( one season during the year) harvest decreases. This may indeed have been the cause of the rise in the rice production during Maha ( another season) 2002/2003 as El-Nino persisted throughout. As with coconut, water harvesting technique was tested to minimize the drought influence. Burring of husk at the root zone of coconut palm, mulching of fertilizer circle at the base of the palm with husk, fallen fronds, loppings of trees like Gliricidiya, Acacia, constructing a small tank at the lower part of the cultivation area for pumping water were some of the methods of rainwater harvesting tested and the result showed that the national average of 7000 nuts per hectare per annum could be exceeded. With the root crop,Cocoyam (Xanthasoma sagifolium) mulching with fallen coconut fronds showed approximately500% yield increase over the control treatment without a mulch It was concluded that hydrological diagnosis immensely helped to develop very promising rain water harvesting technique and minimize the impact of identified drought due to climate change on yield of different crops. Integrated rain water management is the best for coconut palm cultivation. Growing root crops for food security using coconut frond as mulch to alleviate drought. Further inter cropping, planting of trees for shade and as wind belt, breeding varieties of high temperature tolerance were some of recommendations for the adaptation strategies, mitigation options for the agricultural and plantation sectors.
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