Floodplains | Sustainable Development | Water Conservation | Aquifer
Floodplains of rivers have enormous potential for safeguarding sustained water supplies for urban settlements if preserved. Schemes for conserving and connecting these resources need to be encouraged in regions like the Tamirabarani Basin that is facing a water calamity.
Flood plains can help in preserving water. HOW?
•Rivers today are facing complications of terribly low flows due to an indiscriminate extraction of water for use in cities, industries and agriculture.
•Over millions of years, floodplains are formed by the flooding of rivers and deposition of sand on riverbanks.
•These sandy floodplains are exceptional aquifers and any withdrawal is remunerated by gravity flow from a large surrounding area.
•Notably, some floodplains such as those of Himalayan Rivers cover up to 20 times more water than the virgin flow in rivers in a year.
•If we conserve and use the floodplain, it can be a self-sustaining aquifer, and the river and floodplain can be well-preserved throughout.
•Drawing out any more water than is recharged can infect and eventually finish off this precious resource and hence needs to be checked.
•The ‘conserve and use’ principle demands that annual water extraction rate from the aquifer should not exceed the recharge rate.
Potential of River Tamirabarani’s Floodplains
•‘Palla floodplain scheme’ of Delhi Jal Board, covers a 25 km stretch along Yamuna and is already supplying water for over 1 million people.
•Similarly, potential along other rives can be explored to meet the needs of urban settlements in a justifiable manner – and Tamirabarani presents a good case.
•The Potential – Tamirabarani River in Tamil Nadu flows for 100 km through two urban settlements namely – Tirunelveli and Thoothukudi.
•The cities have a population of close to a million people, and the water necessity is less than 54 million cubic meters (MCM) per year.
•Even though 25 Km along the bank has been built over, another 75 Km of the river lies along agricultural land parcels.
•1 km of this 75 Km stretch on both sides of the river can be conserved as a water reservation (floodplains) and used to provide water to towns.
•Specific yield of this aquifer is about 15-20% of its volume and if water is drawn sustainably, it can provide 75-90 MCM of water annually.
•Hence, there is more water than what is needed by these cities, and by contracting a system of wells, this resource can be harnessed.
•If water is metered and priced at the domestic Delhi Jal Board tariff of Rs. 30 per kilo-litre, annual revenue of Rs.162 crores can also be generated.
•Engaging farmers – Conserving the 75 Km floodplain is critical for this scheme, which mandates contracting the concerned farm land owners.
•Farmers in the region are having an erratic income presently, and their holdings can be leased by the government for activating the scheme.
•Such a partnership with farmers will provide them earn a stable income while concurrently retaining ownership rights and preserving aquifer.
•In addition, farmers can actually continue to grow trees for timber, fruit orchards or nut trees on their land (but not water-intensive crops).
•Even the economics of the scheme looks good and the revenue generated by the water board would more than offset the cost of leasing.
Advantages – Economically, a water sanctuary would prevent erosion, rebuild the river ecosystem, and restore the ecological balance in floodplains.
•Even after drawing, floodplains would have enough water to slowly release back into the river in a lean season, which provides the sustenance potential.
•This scheme would also help in curbing illegal extraction of water, curb pollution by industries and encourage better waste management practices.
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