Why Rainwater harvesting is required?Around 300 years ago the Indian sub continent were fully covered with large tress, wild animals and various birds. The human inhabited areas were also having useful tress, plants and domestic pet animals. Cow was an integral part of Indian family as was any other human member in the family. In many places the total number of cattle was more than the number of humans living there. At that time all rivers were perennial. The amount of water flowing in the river remained same during summer as well as rainy season. There were more than 300 thousand tigers and much more other wild animals like leopards, wolves, snakes and elepahnts protecting the forests. The defensive strength of Maratha empire was its dense forests. The wealth of Vijayanagar empire was based on its forest natural resources. The spices of Western Ghats contributed to the vast wealth of Calicut and Travancore.
The Europeans, who came to India as spice traders, slowly started owning the land and the forests were a treasure gold for them. The purpose of building roads, bridges and railway lines during the British Raj was to suck India's natural resources at a faster pace. By 1910 more than 50,000 kilometers of railway lines had been laid and crores of wooden sleepers were used for these. Also the British government auctioned the forest lands to private contracters. The wood from the forests in the Himalayan and Terai regions was also cut and sold in huge quantities for buildings, mines, ships and wars. Tigers, who used to protect the forests, were hunted and killed with the help of Maharajas. The cleared forest land was then used for the cultivation of commercial cash crops.
The monoculture plantations of tea, coffee, rubber, cardamom and various tree species like teak, Casuarina, eucalypts, cinchona, wattle, rubber, clove, pine, oil palm etc, had displaced extensive patches of natural forests throughout the Western Ghats. As per the available estimates the tea plantations had taken away 750 sq km of forest area above an altitude of 1500 m in the Western Ghats. Coffee and cardamom took 1500 sq km and 825 sq km respectively. In Nilgiris around 40% of the land area is under various forms of cultivation. The Plantations tend to be poorer in diversity, particularly endemic species and are hostile to wild species and birds.
Foreign tree species which made an entry into Indian forests more than a century ago have become a serious threat to wildlife as well as the growth of native medicinal plants. The high altitude Shola ecosystem is being threatened by invasive trees like Acacia and Eucalyptus. Wattle was introduced for the extraction of tannin and currently it is a major threat to the sholas and grasslands at high altitudes.
The colonists also introduced non-commercial and aggressive alien plant species during 18th century and 19th century. These exotic Species inhibit the growth of local plants and competes with pastures, crops and native vegetation. Siam weed, considered as one of the world’s worst tropical weeds, is one of the most ecologically destructive invasive plant in the Western Ghats. Siam weed is a prolific seeder. The light seeds equipped with a fine papus can spread all over by wind or water. It can remain dormant for 5 years or more and can establish when the existing vegetation is removed. The plant is toxic to livestock. Siam weed was introduced into India from Central America as an ornamental plant in the 1840s. These invasive ornamental plants had displaced thousands of medicinal plants from our forests
After independence, dams had a significant role in the desertification of the subcontinent. Currently the efficiency of dams are much less than its actual capacity. The Koyna River flows in North-South direction and merges with the East flowing Krishna River. Around 50 thousand million cubic feet of water (TMC) is annually diverted for three private hydroelectricity plants in the Bhima sub-basin, which ultimately flows into the water-surplus Konkan region. The unplanned flow diversions had resulted in the increased flood frequencies at downstream rivers and drought in eastern Maharashtra where continuous stretches of rivers have dried up
The greatest loss is the destruction of many sacred groves that was found all over India. In each state the names given for these groves are different like DeoBhumi (Himachal Pradesh), SarpaKavu (Kerala), Devrai (Maharashtra), Devarakadu (Karnataka), Pavitraskhetralu (Andhra Pradesh), Garamthan (West Bengal), Kovil Kadu (Tamil Nadu), Sarna or Mandar (Chhattisgarh), Umanglai bamboo reserves (Manipur), Jahera or Thakuramma (Orissa), Sarna or Jaherthan (Jharkhand), Law kyntang, (Meghalaya), Gumpa forests around monasteries (Sikkim and Arunachal Pradesh), Than, Madaico (Assam), Devkot or Devsthali (Madhya Pradesh), Devbhumi or Bugyal of sacred alpine meadows (Uttarakhand). The word Sarpa means snake and hence anyone can safely assume that the scared goves of Kerala is the place where snakes can live without fear.
Rain water harvesting will promote more greenery and The conversion of ponds, and lakes into commercial plots had reduced the water retention and increased the chances of flash floods in cities.
Rain water Harvesting (RWH) is the only solution for solving the present water crisis and preventing flash floods. It will also the power bill in agriculture. RWH means collecting and storing of water where it falls, thus preventing the free surface flow of water to canals, rivers and ocean. Soil has the capacity to collect and store rain water - also called Soil Recharge. Like a battery recharges electic charge, soil absorbs water and preserves for a long time. The soil stores water during rainy season and discharges it during summer. Water can be stored in in dams, containers, tanks, ponds etc. But the most cost effective method is to recharge the soil and prevent surface runoff. The runoff of water from higher elevation will cause soil erosion and land slide. The water harvested at high altitudes, drains down due to gravity and finally joins the river
Nature has an evolutionary process, developed over millions of years, for water harvesting. The Himalayan glaciers preserve water as snowpack during winter. During the pre-monsoon season (April-June), the snow melts and creates stream flow. Similarly Kerala and Konkan gets plenty of rain during monsoon. Earlier, the large number of big trees and uneven landscape used tp block the rain water, increasing the soil absorption. Thus rivers in Kerala and coastal Karnataka are called perennial rivers. The trees are essential for ground water recharge and for preventing soil erosion. The importance of Trees is found in Matsyapurana as "A son is equal to ten reservoirs of water and tree planted is equal to ten sons".
The The traditional systems are a replacement for natural systems using trees. When the trees were less, the traditional water harvesting mechanisms like tanks, ponds etc are used to store water for human use. The traditional systems are called by various names like Kulam (Kerala), katta or madaka (Karnataka), Johads (Rajasthan) and surangas (Kasargod). Tank irrigation is common in, Coastal Tamilnadu and Andhra Pradesh, South Central Karnataka, Telengana and Eastern Vidarbha N.E. Uttar Pradesh and Rajasthan.
The real estate boom and dependency on centralized management and distribution of water by government system has resulted in disruption of community participation in water management and collapse of traditional water harvesting system. It became more profitable to convert lakes and ponds into commercial plots. The heavy dependence of water from Dam for irrigation has systematically wiped out the traditional water harvesting mechanisms in Kerala.