Herath Manthrithilake

Simulation model for participatory decision making: water allocation policy implementation in Sri Lanka

This paper describes the value of a computer-based simulation model in the implementation of participatory water allocation policy in Sri Lanka. The model simulates the interconnected networks of 7 basins, including 18 reservoirs, 19 irrigation schemes and 13 hydropower stations. Stakeholders are involved in data collection for the simulation runs, review of the technically acceptable water allocation plan, implementation of the plan and post-implementation review. The modelled nexus captures 72% of the available surface water resources of the island. The result helps to achieve the food and energy security of the country, serving the livelihoods of millions of people.

Hydrogeochemical characterization of Jaffna\u2019s aquifer systems in Sri Lanka

ion from public wells was found to be very low (less than 1 cubic meter (m3)/day (d)) since the method of extraction is purely manual. The average extraction from domestic wells varied within the range of 1 to 1.25 m3/d. Domestic wells with garden usage varied in the range of 2 to 3 m3/d and average abstraction from farm wells for agricultural activities varied from 13 to 19 m3/d (Jeyaruba and Thushyanthi 2009). Punthakey and Gamage (2006) reported that there are 10,263 agricultural wells in the Valikamam area. Therefore, at the above rate, abstraction for agricultural purposes accounts for 164,208 m3/day. In this study, it was observed that abstraction for irrigation varied from 9.4 to 15.7 mm/day with an average of 11.5 mm/day whereas the daily evapotranspiration (ET)7 in 2011 varied from 3.4 mm/day in December to 5.6 mm/day in May 7 Considering the diverse nature of crops cultivated, the non-uniformity in planting dates and presence of perennial crops, crop evapotranspiration (ETc) is assumed to be equal to reference crop evapotranspiration (ETo); in other words, average crop co-efficient (Kc) was assumed to be equal to one. Thus, the notation ‘ET’ is used in this chapter to denote evapotranspiration.

The New Water: Opportunities and Challenges of the Rise to Prominence of Groundwater in Sri Lanka in the Face of Socioeconomic and Climatic Change

Overall high annual precipitation in Sri Lanka belies significant spatial and temporal variation in surface water availability. The ‘dry zone’ comprising two-third of Sri Lanka’s land area receives significantly less rainfall and has high precipitation rates and a five-month dry season. Nevertheless, these regions account for the majority of rice production, the staple crop, thanks largely to the ancient hydraulic civilization based on networks of rainwater harvesting (irrigation) tanks. This manipulation of surface water resources including modern surface irrigation schemes continues to form the backbone of dry zone farming. Groundwater irrigation has remained in the shadows except in the North where surface flows are absent. This scenario is now changing as population growth; poorly maintained infrastructure; commercial agriculture; sectoral competition for water and climate change combine to exert severe pressure on surface water resources. Since the dry zone is also home to a large number of Sri Lanka’s poor households, and a close association exists between high poverty clusters and access to irrigation, the implications of water insecurity for a range of poverty indicators are clear. Not surprisingly, these pressures have prompted an increasing recourse to groundwater in several parts of the dry zone, as governments and farmers recognize the imperative to increase agriculture output, promote crop diversification, and improve agrarian incomes. Yet, with limited groundwater potential, limited detailed knowledge of this resource, and under-developed groundwater-oriented institutions, it is far from certain whether future groundwater exploitation can steer away from anarchy.