Every river flows along the deepest line of its drainage basin which is bound by ridgelines on either side. The aquifers (water bearing sandy layers under ground surface) also slope from the ridge toward river. During rains, the aquifers recharge, and then during the dry season, these aquifers drain into the river, thus keeping it flowing in non-rainy months.
In India, for thousands of years, ponds in the villages and in the fields surrounding them stored rainwater, and then charged the aquifers, besides meeting water requirement of the village. Wells provided drinking water, and to some extent, irrigation.
As the population increased, instead of having more ponds to store more water during rains, we filled even the existing ones, both in the villages and in the fields. We built houses over the filled ponds and started farming on the ones which were located in the fields.
As a result, rain water is not stored, and we have floods of larger intensity. The aquifers are also not recharged, and as a result, do not supply water to the river in the non-rain months. So, the river is in larger floods during rains, and quickly dries after that.
To compound the matters, tubewells have come, which pump water from ever deeper aquifers, taking down the water table, and totally starving the rivers.
Activists have made sure that no dams are built to store water and to use that for irrigation, thus increasing dependency on tubewells.
Lack of industrialisation has made sure that farmers are always more inclined to plant cash crops like sugarcane, which guzzle water. Even in the Kutch district of Gujarat, which has mostly saline water bearing aquifers, sugarcane can be seen planted in oasis which have sweet water, such is the desperation for the cash crops.
In economies which are not industrialised, people earn mostly by exploiting the naturally occurring resources. So we cut trees to earn money, which could have been earned through industries in an industrialised economy. With trees gone, water is not trapped in the forested land, and so aquifers are not charged, and intensity of floods has increased. Forests also create conditions for rains, and with forests gone, rain patterns have changed.
Sand in the river is deposited by water where its velocity is less. So if sand is dredged from a location during dry seasons, area at that spot increases, velocity will be lower, and more sand will get deposited there in the rainy season. But if flood intensity has increased, the water speed may remain higher, and sand may not get deposited, and will instead be taken downstream and deposited close to sea, or may be washed into sea.
And so, the activists have found a solution: ban sand dredging. And our dumb ruling class has surrendered. And therefore we are now planning to import sand.
The real solutions instead are:
1. Restore all ponds/dig new ones.
2. Build big storage dams, and replace tubewell irrigation with canal irrigation. That will recharge aquifers, instead of draining them.
3. Industrialise India, so that the mad rush to plant water guzzling cash crops is given up, and people do not cut trees to earn some money today, and more forest areas are not cleared and brought under farming.
4. Make water harvesting a mission, with the target that no rain water flows into sea. For that, instead of harassing existing home owners, construct big ponds close to rivers all along them, and divert rain water from rivers into them.
5. Stop outsourcing policies to the thuggish activists. If hydrologists from our reputed engineering colleges were consulted, they would have prescribed above steps outlined from 1 to 4 only.
6. There is no need to ban sand dredging from rivers. It is counterproductive. Instead, consult hydrologists to prevent over-exploitation at any particular spot. Better housekeeping, which is desirable, must not be confused with outright bans, which are idiotic.
Water crisis is looming, and instead of wasting time and diverting attentions in stupidities like bans on sand dredging, efforts and resources must be spent on that which will actually give us more water and keep our rivers healthy : in increasing water storage and better water usage.