The groundwater resources is one of the most important National Assets of our country and it holds one of the key to our Nations’ Economic prosperity. Since the availability of this groundwater resource is vary from place to place and need for proper and careful planning, development, conservation and use with utmost care to the growing demands in Agriculture, Drinking water, Industries and other requirements.
The main objective of the Hydrogeological division is to development and management of Groundwater Resources in environmentally sustainable manner to uplift the socio-economic standard of the people of Sri Lanka. On the requests of various Government Institutions, Non-government organizations and Individuals, following groundwater development activities are carry out by the hydrogeological division. All the regional offices, chemical laboratories, are come under the hydrogeology division.
Activities
The following scientific methodologies are used to perform the above activities.
- Geophysical Surveys (ID and 2D surveys)
- EIA surveys
- Pumping tests
- Water Sampling and well monitoring
- Borehole logging
Geophysical Investigations
Resistivity method is one of the most prominent survey techniques on the evaluation of the subsurface topography and the occurrence of deep and shallow groundwater resources. Geophysical surveys were conducted using resistivity method to understand the subsurface water bearing capacities, overburden and depth of the hard rock formation. The occurrence of deep groundwater is mainly depending on the extent of weathering and fracturing in deep hard rock formation. Therefore, quantity of water that can be extracted from ground varies from place to place.
- 1D resistivity survey
The aim of the 1D resistivity survey is to determine the sub surface conditions including structural weak zones, thickness of soil overburden, weathered rock and to observe changes in the quality of groundwater with depths. Water Resources Board carry out 1D surveys in order to study the subsurface conditions in detail. The high-end instruments use to obtain the apparent resistivity values of the sub surface formation according to different electronic configuration (Slumburger, Wenner, etc.)
- 2D resistivity surveys (Electrical resistivity imaging (ERI)
Electrical resistivity tomography (ERT) or electrical resistivity imaging (ERI) is a geophysical technique for imaging sub-surface structures from electrical resistivity measurements made at the surface, or by electrodes in one or more locations. If the electrodes are suspended in the boreholes, deeper sections can be investigated. A related geophysical method, induced polarization (or spectral induced polarization), measures the transient response and aims to determine the subsurface chargeability properties.
The AGI SuperSting R8/IP earth resistivity meter is the instrument use for 2D resistivity surveys of Water Resources Board. This instrument is use for resistivity & IP imaging in applications such as groundwater exploration, geo-technical & engineering investigations, horizontal drilling, mapping of pollution plumes, cavity detection, archaeological and environmental work etc.
EIA Survey
Environmental assessment (EA) is the assessment of the environmental consequences (positive negative) of a plan, policy, program, or actual projects prior to the decision to move forward with the proposed action. In this context, the role of Water Resources Board is to consider about the hydrogeology of the area and detect the impact for the groundwater as a result of implementing specific projects or actions. Here, it’s consider about the current hydrogeological environment and give recommendations for protection, conservation, minimizing the negative impacts and sustainable development of hydrogeological setup of the area including ecology and sociology. Environmental assessments may be governed by rules of administrative procedure regarding public participation and documentation of decision making, and may be subject to judicial review.
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Pumping Tests
A pumping test is conducted to evaluate the amount of water that can be pumped from a particular water well. More specifically, a well test will allow prediction of the maximum rate at which water can be pumped from a well, and the distance that the water level in the well will fall for a given pumping rate and duration of pumping.
Well testing differs from aquifer testing in that the behavior of the well is primarily of concern in the former, while the characteristics of the aquifer (the geological formation or unit that supplies water to the well) are quantified in the latter. When water is pumped from a well the water level in the well falls. This fall is called drawdown. The amount of water that can be pumped is limited by the drawdown produced. Typically, drawdown also increases with the length of time that the pumping continues. According to the well type and flushing yield of the well, the duration of the test may vary as 6 hours, 24 hours, 48 hours and 72 hours.
Well Monitoring and Water Sampling
Designing of groundwater monitoring networks and conducting groundwater monitoring programmes with special reference to water quality and water levels of periodical reports related to water resources. These water level measurements were used to understand the fluctuation of groundwater table
Borehole Logging
Logging of boreholes to investigate the sub surface strata.
