Here’s a simplified understanding of Springs in the Nilgiris, particularly the upper areas.
What are Springs?
Springs are places in the soil or rock where groundwater emerges naturally. This could be a single point or a set of points close to each other. Springs that flow throughout the year are called perennial springs, whereas those that dry up for some time each year are called seasonal springs.
Springs and People
In the hills many old villages were located close to springs. Even today a good number of villages in the hills depend on springs for their water supply, either as the only source or in addition to other sources of water such as wells, streams etc. Often when streams or wells dry up in summer, people depend on springs to provide clean drinking water. Realising the importance of springs in their lives, many local communities have springs as part of their cultural and religious practices. It is not uncommon to see a small shrine or a temple next to an important spring.
Springs and the Environment
Springs are the sources of all rivers and streams in the southern hills. In the absence of glaciers that feed the northern rivers, the dry season flows in southern rivers are maintained by springs. By slowly releasing the water stored in aquifers into the streams and rivers, springs ensure that various forms of life including humans are able to survive even when there are no rains for prolonged periods. Wildlife too depend on springs for drinking water when the streams and water bodies dry up and this often leads to conflicts with people.
Common types of Springs
Springs can occur when the water table cuts the surface of the earth (depression spring), when one water bearing layer meets a layer like hard rock or clay that does not allow water to permeate (contact spring), when there are fractures in hard rock (fracture spring), cavities in limestone (karst spring) or along faults in the rock structure (fault spring). In nature sometimes a combination of such springs may also occur.
Springs are affected by rainfall pattern, land use patterns in the springshed and the nature of the aquifer feeding the spring. The key parameters to be monitored in springs are discharge (in liters per minute) and water quality (pH, Total Dissolved Solids, Nitrate, faecal coliform etc.). Where possible, discharge can be easily measured using a bottle or bucket of known volume and the time taken to fill it can be recorded with a stop watch. This measurement can then be expressed in liters per minute through a simple conversion.
From one year to the other change in rainfall pattern can affect the discharge pattern of springs. Therefore it is important to measure daily rainfall data for a location at or near the spring. By combining the discharge data and rainfall data, a spring hydrograph can be prepared that can help us understand the aquifer characteristics and impacts of any interventions being made in the springshed.