Surface Water-Ground Water Interactions: The Curious Case of Ponds

[00:00:03]Dear colleagues, good morning. Today we are going to talk about groundwater surface water interactions. One of the most fascinating topics in hydrarology yet one of the least researched topics.

[00:00:14]Because of this there are lots of misconceptions about this among the water professionals. Today we are going to discuss this interesting thing its theoretical applic aspects and its practical application for solving a real life problem in the water sector. First of all, there are two ways in which groundwater surface water interaction happens in the field. In the first case, groundwater contributes to flows and surface water bodies such as rivers, streams, lakes and ponds. This is how many monsoon fed rivers get the flows during the summer season. A good example is the god river in south India. In the second case, streams contribute to groundwater recharge. An irrigation pond is a good example of shallow groundwater contributing to surface water bodies.

[00:00:55]Let us look at a classical pond in a high rainfall area. These ponds normally do not receive any runoff from the surrounding area. Normally the agricultural fields. Now how do we distinguish them from tanks irrigation tanks for the water levels in the ponds fluctuate in the same manner as the water levels in the wells in the surrounding area fluctuates. These are common in the high rainfall areas of countries such as Sri Lanka, India, Cambodia and Bangladesh. Interestingly, I have seen many situations in India where and in some of our neighboring countries where these ponds are now being treated as rainwater harvesting systems. A lot of money is being spent by national and local governments to subsidize farmers to dig out ponds in their farms. The water agencies also invest a lot of money to rehabilitate such ponds that exist in the common land. The underlying assumption is that they could add to the water supplies and reduce the pressure on groundwater resources for irrigation and other uses in the rural areas. In reality, such ponds do not augment any water supply locally. Instead, they make it easy for the farmers to tap underground water easily. The result is faster exploitation of groundwater resources.

[00:02:06]The best way to distinguish the ponds from the conventional irrigation tanks is to look at the water table of the surrounding area. If they correspond that means the ponds receive water from the shallow acif of the area. This is just one simple example of groundwater surface water interactions. To know more about groundwater surface water interactions in a river basin context, please watch the next video. Thank you so much.