Report of the Western Ghats Ecology Expert Panel - Part II : Human Pressure and Ecological Impacts : 3. Issues of Concern - Forest destruction in the river catchments

Opinion
       13/11/2018
                1540.

SUB : Report of the Western Ghats Ecology Expert Panel - Part II : 3. Issues of Concern - Forest destruction in the river catchments

REF : 3. Issues of Concern - Forest destruction in the river catchments

Issues of Concern :

Forest destruction in the river catchments :

Western Ghats has a long history of deforestation. Deforestation of upper catchments of rivers for timber, river valley projects and plantations has drastically reduced the capacity of the hill streams that feed into the rivers to hold and recharge water. Drying up of streams immediately after the monsoons and desiccation related to deforestation is clearly evident. This in turn has contributed to reduced summer flows.

River management in the Western Ghats :-

Most of the rivers in the Western Ghats are either dammed or diverted, some of them at several sites for power generation in the upper reaches and irrigation in the lower reaches. For instance, the east-flowing tributaries of Cauvery (Bhavani, Moyar, Kabani) and Krishna (Bhima, Tunga, Bhadra) are already dammed. The west-flowing shorter rivers (Sharavathi, Periyar) have been dammed at several places. We also have complete diversion of river flows at Mullaperiyar and Parambikulam dams involving Kerala and Tamil Nadu. West- flowing rivers have been virtually made into east-flowing rivers by violating all natural laws.

Dams are without dispute the most direct modifiers of river flows. They can heavily modify the magnitude (amount) of water flowing downstream, change the timing, frequency and duration of high and low flows and alter the natural rates at which rivers rise and fall during runoff events. Severe daily flow fluctuation between peak and off peak times below dams is commonplace in west-flowing dammed rivers. This has impacted drinking water schemes, major and minor irrigation projects operating in downstream areas apart from cutting off flood plains and impacting aquatic ecology and riparian systems. However very few studies are available that correlate the reservoir operations with the different types of downstream impacts and put measures in place for mitigation.

In the case of inter-basin water diversions, absolutely no natural flows or even ‘minimum flows’, leave alone environmental flows, are left below the dams. The Mullaperiyar dam is a classic case where the main tributary of Periyar has been completed diverted to the Vaigai basin in the east. Idukki dam does not even have a spillway for allowing monsoon spills into the river. In Maharashtra, the tail race discharges of Koyna Powerhouse I, II and III are released into the west-flowing Vashishthi River and lead to heavy floods in Chiplun. Continuous stretches of rivers have dried up irreparably below diversions affecting river ecology, surface flows and even ground water seepage.

Many of the reservoirs especially in the steep valleys are silting up prematurely due to the massive encroachment and deforestation of catchments consequent to dam construction. Idukki dam is a classic case wherein the entire catchment was encroached along with dam construction.

The operations of hydro electric stations (reservoir operations) are in tune with the power needs rather than the downstream water needs. Hence daily flow fluctuations created by peak and off peak operations of reservoirs in dammed rivers have led to upstream–downstream conflicts in many river basins. Similarly diversion of flows into another river basin after power generation is creating problems of daily flood in the recipient basin and drought in diverted basins. These are turning into management issues which need to be addressed at a basin level. However, there is a lack of systematic river basin level data on ecological changes due to hydrological alterations created by dams.

Incorrect land use patterns :-

Mining for mineral ores, granite and lateritic mining has affected water availability and recharge especially in the lower altitude regions and midlands. In Goa alone, the government itself has acknowledged that over half of the 300 odd mining leases are located close to water bodies. Data tabled in the Goa Assembly revealed that several of the 182 mining leases exist within one kilometer of a major irrigation project, the Selaulim dam, which provides drinking water to six lakh people in south Goa, virtually half the population of Goa.

(Ref:http://www.deccanherald.com/content/85522/182-mining-leases-goa-near.html).

In South Karnataka and North Kerala, surangams–a traditional irrigation system in lateritic hills is losing out to lateritic mining. Many of the rivers in this region originate from these lateritic hills and many of the Western Ghats Rivers like Chandragiri, Valapattanam, and Netravathi benefit from the water recharged by lateritic hills in their flow downstream.

Agricultural practices including cropping patterns have a role to play in water resource management in the Western Ghats. Planting steep slopes with soil-eroding monocu;ture crops like rubber and banana, and heavy tillage, has led to increased surface runoff along with loss of precious top soil. This has contributed to low seepage and infiltration into deeper soil depths. The deforestation for tea, coffee and cardamom plantations located at higher altitudes has contributed to drying up of hill streams.

Reclamation of high altitude valley swamps is contributing to water scarcity in the upper catchments. Many of the rivers originate from these swamps and are source of perennial flow. In the Nilgiris, most of the fertile water rich swamps have been converted for intensive pesticide-based farming, greenhouse farms, housing, etc.

NEXT : Sand mining

To be continued ..

JAIHIND
VANDEMATHARAM