Groundwater quality in the Valigamam region of the Jaffna Peninsula, Sri Lanka

Abstract

The Valigamam region is underlain by a Miocene limestone formation and a highly porous soil cover. The region is totally dependent on groundwater to meet its agricultural, industrial and domestic needs, since other sources of water are seasonal. Recharge from rainfall is limited by high run-off and evapotranspirational losses. The region experiences water supply problems due to high concentrations of chloride, total hardness and nitrate in groundwater. The spatial distribution of chloride varies from year to year, with maximum concentrations experienced during or after the wet season. The major factor explaining high chloride concentrations is the excessive extraction of groundwater that results in saline intrusion from the sea or tagoonal areas. In a large proportion of wells sampled for nitrate, levels exceed the WHO standard due to intensive agricultural practices involving very high inputs of artificial and natural fertilizers and the improper construction of latrine soakaway pits. To improve groundwater quality in the Jaffna Peninsula will require controls on the location of new wells, a revision of existing and future pumping rates and a change in agricultural practices. It is imperative that future work in the region should focus on combining groundwater management and sustainable agricultural practice.

Simulation of Potential Groundwater Recharge from the Jaffna Peninsula of Sri Lanka using HYDRUS-1D Model

“…The HYDRUS-1D simulated potential groundwater recharge was 41.8 cm per year. This is 30-35 percent of the annual rainfall, in agreement with the estimates of Rajasooriyar et al (2002) for the study area. The recharge calculated by the WTF method based on measured groundwater levels was 29.8 cm.…”

“…Year 2007 was a normal year with an annual rainfall of 1291 mm compared with other years, for example 2008, where the rainfall was higher than the average. The mean annual rainfall in the Jaffna Peninsula is approximately 1255 mm (Rajasooriyar et al, 2002). In the years 2008 and 2009 the annual rainfall was higher than in 2007.…”

“…In the north-east the limestone scarcely crops out, but there are a number of karstic features including surface depressions (e.g at Manipay Idikandu), tidal wells (Puthur Nialvarai), cliffs and springs (Keerimalai). The limestone is generally overlain by highly porous thin (maximum 2 m) soil cover of red earth (Rajasooriyar et al, 2002).…”

Assessment of Groundwater Resources in Jaffna Limestone Aquifer

“…Continuing overdraft exceeding the safe yield may subsequently lead to progressive decline in groundwater table in the study area. This result had been supported earlier by Rajasooriyar et al (2002) where the groundwater level patterns for the period from 1979 to 1997 show differences in water level elevations by increasing the area of negative level elevations. Authors mentioned that excessive extraction of groundwater from wells, particularly from agricultural wells using highly efficient electrical pumps for prolonged periods, was the main course of the reduction in groundwater elevations.…”

“…The estimation of annual water balance is critical for water management and development planning. Rajasooriyar et al (2002) reported that water shortage is a major problem and groundwater often serves as an important and safe source of water for the Jaffna Peninsula in Sri Lanka. The water resources of the basin remain almost constant while the demand for water continues to increase.…”