There has been substantial increase in the level of carbon dioxide and other gases in the atmosphere, especially over the last one decade. And these gases have been observed to induce severe changes in the climate and accelerate global warming across the world. We all know that the global average surface temperature has increased significantly in last nearly hundred years and the projection of several research and ecological studies firmly point out that in coming hundred years the Earth will experience high surface temperatures. Looking at the current situation, a number of physical and biological systems in different continents are being affected to a larger extent, due to climate change, than it was thought to be. Several research and studies carried out across the globe have time & again confirmed that greenhouse gas emission due to anthropogenic activities is changing the average global temperatures which have been disrupting the global hydrological cycle. And this is directly and indirectly affecting every aspect of human life and survival.
The hydrological cycle is one of the most important components of the worldwide climate system which plays a pivotal role in distributing and re-organizing the sun's energy throughout the globe. The modifications in the global hydrological cycle due to climate change including drought, flood, erratic rainfall, extreme weather conditions and changes in river flow and groundwater resources have been observed in various parts of the world - rise in sea level by nearly 20 cms; 45% of Arctic sea ice melting within 50 years; increase in discharge of rivers in to the Seas and the like. Some research studies have also showed that overall surface water runoff increases by more than 6% in case of just 1°Centigrade rise in global temperature.
It has been observed that global mean sea level has risen by nearly 1.0 meter since the beginning of the twentieth century. In addition to this climate change has already affected various ecosystems particularly due to sea-level rise and changes in runoff patterns. Some studies have also indicated that nearly 40% of the world's population will be directly affected due to sea level rise by 2050 as they are in the immediate vicinity of the coast.
Research studies in India have shown that climate change will severely impact freshwater resources due to changes in rainfall pattern, rising surface temperature, changes in groundwater recharge, increased evaporation and the like. It has been observed that the surface temperature of the Indian subcontinent has risen by half a degree centigrade over the last 100 years. Drastic changes in rainfall pattern has been observed in India wherein the average rainfall deviated from about 5% to 17% than the normal rainfall pattern. It can be stated that changes in surface runoff over the Indian subcontinent would certainly increase by up to 25% in the coming 50 years.
These reports and studies definitely indicate that climate change has largely influenced the water resources of the Indian subcontinent in a major way. Additionally, it is clearly visible that water demand for various sectors such as industrial, agricultural, domestic and other purposes has drastically increased in last four decades. It is a known fact that In India, all the major and minor rivers are the only freshwater resources that meet the water demands for agriculture, domestic and industrial purposes. Out of the annual flow of Indian rivers, which is about 1,880 km3/year only 40% of the total flow is utilized to meet the water requirement for agriculture, domestic and industrial purposes. Consequently, expansion of agricultural sectors, land use pattern, industrialization, growth of urban centres and other developmental projects are affecting the global hydrological cycle. This is in turn affecting the per-capita water requirement which is gradually increasing. It has been observed that the rain received between September 2018 and February 2019 was less than 50% of that in 2017 - 18, which only points towards severe water scarcity in the coming days.
Thus, it is extremely important to re-design our economic policies and restructure the development framework which needs to incorporate sustainable modules and ecologically sensitive outlook.
