Portal de Periódicos da CAPES

Water Resources

2023; Springer Nature; Linguagem: Inglês

10.1007/978-981-99-1843-0_4

2198-3542

Ashoka G. Dessai,

Flood Risk Assessment and Management

The erratic distribution pattern of precipitation, demographic pressures and increased anthropogenic activity have taken a toll of the hydrological environments of Goa. The declining trend and degradation of groundwater is a cause of serious concern that needs urgent attention. Three lithological types characterize the groundwater aquifers in the State, namely (i) the lithomarges beneath the laterite duricrust, (ii) sandy alluvial-colluvial deposits of the coastal plains that abut against the lithomargic aquifers and (iii) weathered and fractured country-rock metasediments/granitic gneisses. The first is an unconfined aquifer, the second is a semi-confined aquifer whereas the third is a confined aquifer. The presence of intercalated clays/lithomarge horizons, at places, gives rise to sub-artesian conditions. The annual precipitation in Goa varies from 3000 to 3800 mm. The water potential of the State is placed at 85.70 Mm3 of which nearly 40% goes as runoff. Irrigation accounts for 146.50 Mm3 of which 112.50 Mm3 is contributed by surface water and 34.00 Mm3 from groundwater. The water requirement of the State is 1329 Mm3. In comparison with the water level of the previous decade (2005–2015), a declining trend of watertable is noticed in the northern, central and western parts of the State. The eastern talukas namely Bicholim, Sanguem and Valpoi, which host the iron ore mining belt, exhibit recession in watertable due to dewatering of the mines. Positive impact on the groundwater table is also observed in some parts of these talukas as a result of secondary recharge due to the return flow. Increased anthropogenic activity has had an impact on the groundwater quality whereas excessive withdrawal has resulted in saltwater intrusion in coastal areas. The chapter reviews the experiences and strategies of efficient utilization of water resources and recommends actions for mitigation to control overconsumption of the resource from increased demographic pressures. Efficient ways of rainwater harnessing and water conservation initiatives are discussed to relieve pressure on the groundwater resources and to keep pace with the increasing demand for ensuring sustainability of this fundamental component of the economy.