Significance of Isotopes Based Studies for Climate Resilient Groundwater Management Prof. Partha Sarathi Datta In many parts of the globe, the actual distribution of the abundant water in the perennial resources, over space and time, is strongly influenced by climatic and geographic factors, and land use, and freshwater crisis and water resources management problems exists in many parts of urban, peri-urban and rural areas at different times of a year. A glance at the water situation suggests that in many parts, due to increase in water demand, zonal disparity and inadequate availability of surface water supply, its annual exploitable groundwater potential of will continue to be used intensively. The anticipated climate change impact is therefore a concern of vital importance for safe water availability to all socio-economic sectors development. Although, there are considerable uncertainties associated with the predictive models on climate change, yet, the projected increase in population by 2025 is likely to drop the per capita fresh water availability to levels of water scarcity. For a climate resilient water management in the long term, the groundwater managers may be confronted with some of the important aspects such as, characteristics of groundwater renewal, its flow velocity and direction, interaction with each other as well as with surface water, the sources and dynamics of pollutants and containment of their spreading from known sources, and the causes of its quality deterioration, under both the steady and non-steady conditions. Generally, the conventional studies on regional flow systems adopt the approach based on gravity-induced flow from high to low head, which provides a short-term feature of the hydraulics. The mechanisms that govern water demand are not well outlined. The knowledge of the aquifer systems and management practices that can help reduce the impact are often limited at the level at which a management response is required. In this context extensive field investigations were carried out by my team and me, for over four decades in different parts of India under semi-arid and arid conditions, using radioactive (3H, 14C, 234U, 238U) and stable (2H, 18O) isotopes. Mean recharge in river basins has been estimated using tritium injection technique by tracing soil moisture movement. Regional groundwater residence time in the aquifer and flow velocity has been estimated by 14C (T1/2 = 5730 yr) ages of groundwater. Groundwater seepage loss has been assessed using seasonal variation of 18O/16O and 234U/238U isotopic ratios and 238U concentration in groundwater and river water, representing varying components of overland and subsurface flow. 2H/1H and 18O/16O ratios have been used for detailed insight into the groundwater recharge and contamination characteristics, flow regime, flow-pathways and mixing in groundwater system. Potentials of isotope techniques based on my own four decades of experience (although may not be comprehensive) provided a direct insight into the water dynamics and distribution within hidden groundwater aquifers system, and proved to be very useful for groundwater management.
Taxonomy
- Groundwater
- Water Management