It would appear that with about 3m of annual average rainfall and a variety of natural and man-made freshwater sources, Kerala, is a land of surplus water. But, studies by reputed research institutions in the State reveal that Kerala is no ‘safe state’ as regards fresh water availability. Ensuring uninterrupted year-round fresh water supplies remains the greatest challenge to water managers owing to high human stress in this densely populated State.
Although Kerala receives a large amount of rainfall, its distribution is erratic. Storing the water in surface and subsurface, natural and man-made reservoirs seems an attractive solution. However, rapid economic growth and human interference in the past 3-4 decades has deteriorated the capability of hills, forests, and wetlands to serve as water reservoirs for the population. This has a telling effect on the availability of water during summer. The scenario is grim between January and May, when most irrigation needs are to be met, salinity intrusion is to be arrested, hydel power has to be generated and drinking water scarcity is acute.
The total discharge of water in all the 44 rivers in Kerala together amounts to 77,900 million cm (mcm). This figure is only about 75 per cent of the water discharge of a single major river like the Godavari. Thus, despite the presence of so many rivers in Kerala, it is no guarantor in terms of freshwater availability.
In fact, studies by N M Basak, Former Executive Director, Centre for Water Resources, Development and Management, prove that freshwater availability in Kerala is lower than that in neighbouring Tamil Nadu and Karnataka. High population density, rapid economic development, higher per capita consumption of water in Kerala (160 litres per day) compared to the national average (135 litres per day), higher level of personal hygiene, poor water resource development have combined to bring in a problematic mismatch in the demand and supply of water in Kerala. Of late, indiscriminate sand mining along rivers and sea coasts has contaminated fresh water resources such as wells, and has made matters worse.
Kerala’s freshwater resources
The prime source of fresh water in Kerala is rain— about 3062 mm annually, which is about 2.5 times more than the national average. About 60 per cent of the annual rainfall comes from the southwest monsoon (June to August), while 25 per cent comes from the northeast monsoon (September to November) with the remaining coming from sporadic spells throughout the year. However, the steep and undulating topography causes a major portion of the rainwater to drain out into the sea through rivers and groundwater pathways.
Kerala has 41 west flowing and three east flowing rivers. But, all the rivers are short, with catchment areas less than 6200 sq km. As per national norms, Kerala does not have a single major river. There are only four medium-sized rivers (Chaliyar, Bharathapuzha, Periyar and Pamba), with a total drainage area of 16,742 sq km. The remaining 40 are minor rivers with a total catchment area of 19,489 sq km (much less than the catchment area of any major Indian river). The total discharge of all 44 rivers comes to about 77,900 mcm. With erratic rainfall, and uncertainty rife in water availability, rivers in Kerala have been dammed in many parts for irrigation, power generation and drinking purposes. At present, Kerala hosts 32 reservoirs of variable dimensions in its uplands. Most of these reservoirs were commissioned in the second half of the 20th century.
In addition to these, Kerala has several lakes, the important ones being Sasthamkotta, Vellayani and Pookode. Unfortunately, anthropogenic factors and human interference have caused many lakes along the coastal region to degrade, with water levels dropping over the years, notwithstanding steady and substantial rains. This is a problem that needs careful evaluation given the fact that the lake system is the lifeline for several lakhs of people in Kollam town and adjoining areas. Recently, lake Sasthamkotta was declared a Ramsar site, to protect it from further degradation and encroachment. The State also has a total of 837 private, 746 panchayat and 632 holy ponds. Only about 15 per cent of these, though, are currently in use for domestic water supply or for minor irrigation schemes. In addition, there are about 270 pit lakes that have resulted from mining and quarrying activities. Kerala has about 212 irrigation tanks. The total water spread of all the ponds and tanks comes to about 65200 hectares.
Apart from all these sources, Kerala is endowed with many springs. A survey conducted in 2010 by the Centre for Earth Science Studies (presently NCESS) in the coastal lands of Thiruvananthapuram and Kollam districts revealed that the region had 204 springs. The combined water potential of the springs is estimated to be 125 lakh litres a day, which is enough to meet 15.26 per cent of the water demand in 35 panchayat and three municipalities falling within the area covered by the study.
With most homes equipped with wells, it is a major source of potable water in the State. Open wells, filter point wells and tube wells are major ground water extraction structures in the State. Kerala hosts over thirty lakh dug wells with a well density varying between 100 and 250 wells per sq km. Over 90 per cent of the wells are used for drinking purposes, with a traditional dug well capable of yielding 10-20 cubic m of water per day.
Of late, wells in the State are getting increasingly contaminated. Microbial pollution is the major source of contamination, and the cause of water- borne diseases in Kerala. A paper by Harikumar et al., 1995, ‘Dispersion of domestic pollutants in ground water sources of Palghat district of Kerala’, from the Centre for Water Resources Development and Management (CWRS) has revealed
that more than nine lakh people are annually affected in Kerala by water-borne diseases owing to this problem.
To counter this menace, the government of Kerala has already embarked on a chlorination programme with the help of local women’s organisations. Volunteers not only train households’ members about well maintenance, but also teach them how to chlorinate water, and refrain from using it until two hours after. Recently, water cards have been introduced by the CWRS in collaboration with local self governments for household wells. These water cards list all relevant details relating to water quality parameters, mentioning water quality standards, with required treatments necessary to improve the quality. Currently a pilot project, it is slated to be upscale to cover every household in the State.
Impact of sand mining on surface and ground water sources
Unscientific human intervention in the form of careless quarrying of soils, levelling of hillocks, deforestation, reclamation of wetlands, sand and clay mining from flood plains, and indiscriminate sand mining from rivers and beaches have aggravated water scarcity in coastal Kerala. According to ecological researcher Dr A D Shobana Raj, nearly 80 per cent of the water resources in coastal areas have become saline, making matters extremely difficult for the resident population.
Indiscriminate sand mining adversely affects the quality and quantity of both surface and ground water sources. Rivers subjected to intense sand mining exhibit overloading of suspended particulates, besides marked changes in pH, electrical conductivity, and deposition of sulphates/iron in the overlying waters. Channel incision consequent to sand mining can accelerate the lowering of ground water tables in areas close to river channels. A study carried out in Achankovil river basin draining through the Pathanamthitta district of Kerala revealed that mining induced channel incision and subsequent changes in the groundwater table primarily accounted for the drinking water scarcity in the area. Out of the total 53 wells studied in the Thumpamon Gram Panchayat in the Achankovil river basin, 36 per cent are perennial and 64 per cent seasonal. Most wells that dried up in summer were the older ones. A similar scenario prevailed in the lowlands and midlands of the Manimala river basin as well. Out of the 90 wells surveyed (NCESS), 65 per cent dried up in summer. The majority of the wells in this category were older and perennial prior to the onset of indiscriminate sand mining.
Deepening of wells in the flood plains was inevitable for ensuring continued water availability. It is estimated that the riverbed in the surveyed stretch had lowered by about 2 m with respect to the level in 1990. Another adverse effect of river bed lowering is that it reduces the flood pulse events in the riparian wetlands in high flow regimes, mainly because of the increased height of the river banks due to channel incision resulting from mindless sand mining. This automatically leads to drying up of riparian wetlands. Water level lowering and deepening of master channels can also reduce the gradient between the master channel and riparian wetlands and/or floodplain lakes. The best example is Sasthamkotta where indiscriminate sand mining in the Kallada River and its flood plains has significantly reduced the subsurface movement of water towards the lake system. Lowering of the river channel also aggravates salt water intrusion in river mouths. A 2012 study carried out in the Muvattupuzha river, by K Maya, Senior Scientist, NCESS, reported high concentrations of Ca, Mg, Na, K, and Cl in the water samples collected from the flood plain pits left after sand mining using high power jet pumps. The results of the study reiterated that the ground water resources in many stretches along the lower reaches of the Muvattupuzha river had been destroyed due to saline intrusion.
Sand mining from beaches along this coastal State is directly responsible for the collapse of beaches all along Thiruvanthapuram and several coastal districts. When beaches collapse due to indiscriminate mining of sand, there is no barrier left between the sea and the groundwater reservoirs that feed wells and water bodies. Saline water from the sea rushes in and contaminates the groundwater, and destroys wells and other freshwater resources. Collapsed beaches result in the sea moving inland, and destroying fishing villages. This is a major cause of concern in this coastal region, especially since it has resulted in thousands of fishermen and fish-workers becoming environmental refugees.
Problems plaguing Kerala’s water resources
Analysis of available data reveals that during the last 100 years, while the per capita rainwater availability in India has decreased fourfold, the respective drop in Kerala is five fold. Meanwhile, the demand for water has been rising exponentially over the years. It is estimated that while the demand for fresh water in the state in 1901 was 1026 million litres, it rose to five times to (5342 million litres) by 2011.
A few important measures could be adopted for judicious management of fresh water in the State. Firstly, water storage capability of natural (soil, sub-soil, wetlands, forests) and man-made (dams, ponds) systems ought to be enhanced to the best possible level. Then, residence time of water in the terrestrial environment needs to be enhanced to improve the rate of infiltration/percolation into subsurface formations followed by efforts to bridge the gap between demand and supply of drinking water by finding new sources of water (i.e., non-conventional sources) and reducing the loss and leakage of fresh water during the transfer and end use phases. Also there is an urgent need to evolve strict norms for utilisable water resources and use of high quality water should be avoided for irrigation. An immediate ban on direct disposal of liquid and solid waste into rivers and reservoirs must be put in place and scientific waste management to minimise pollution of urban water bodies must be adopted. Application of chemical fertilisers in agricultural lands must be minimised and organic methods for agricultural productivity promoted. A limit to the extraction of sand within the land’s carrying capacity must be put in place. Also suitable engineering structures must be constructed, such as check dams in upstream areas to reduce run-off and siltation. Finally, the right to drinking water for the economically poor must be ensured and awareness created on the finite nature of water at all levels.