Day 73 – Q 4.Examine the adverse impacts of excessive sand mining on the river ecosystem.

4. Examine the adverse impacts of excessive sand mining on the river ecosystem. 

नदी पारिस्थितिक तंत्र पर अत्यधिक रेत खनन के प्रतिकूल प्रभावों की जांच करें।

Introduction:

Sand mining is a practice that is used to extract sand, from various environments, such as beaches, inland dunes and dredged from ocean beds, and river beds of deltaic regions. Today, demand for sand and gravel continues to increase. By 2020, 1.4 billion tonnes of sand will be required in India. Sand mining is thus a lucrative business and fuels illegal extraction. Illegal and unscientific sand mining is turning out to be one of the biggest ecological disasters in modern India.

Body

• Sand is vital for sustenance of rivers. River supports an extraordinary array of species, many of which are under threat due to habitat destruction. During the past 3-4 decades, river systems of the world have been altered significantly due to indiscriminate sand mining. Sand mining has many deleterious direct and indirect effects on the physical, chemical and biological environments of river systems. 
• Excessive sand mining can alter the river bed, force the river to change course, erode banks and lead to flooding. It also destroys the habitat of aquatic animals and micro-organisms besides affecting groundwater recharge.
• Depletion of sand in the streambed and along coastal areas causes the deepening of rivers and estuaries, and the enlargement of river mouths and coastal inlets. It may also lead to saline-water intrusion from the nearby sea. The effect of mining is compounded by the effect of sea level rise. Any volume of sand exported from streambeds and coastal areas is a loss to the river ecosystem.
• Sand mining disturbs the equilibrium of a river channel because it intercepts material load moving within a dynamic system and triggers an initial morphological response to regain the balance between supply and transport. Channel widening causes shallowing of the streambed, producing braided flow or subsurface inter-gravel flow in riffle areas, hindering movement of fish between pools. 
• It is now widely realized that, in spite of the short term benefits, the indiscriminate sand mining from the rivers is detrimental to these life sustaining systems, in the long run. Moreover, the effects of instream sand mining may not be visible immediately because it requires continuous monitoring and takes a decade or more to surface and propagate the effects along the river channel in measurable units.
• Mining which leads to the removal of channel substrate, resuspension of streambed sediment, clearance of vegetation, and stockpiling on the streambed, will have ecological impacts. These impacts may have an effect on the direct loss of stream reserve habitat, disturbances of species attached to streambed deposits, reduced light penetration, reduced primary production, and reduced feeding opportunities.
• Sand-and-gravel mining in stream channels can damage public and private property. Channel incision caused by gravel mining can undermine bridge piers and expose buried pipelines and other infrastructure.
• Apart from threatening bridges, sand mining transforms the riverbeds into large and deep pits; as a result, the groundwater table drops leaving the drinking water wells on the embankments of these rivers dry. Bed degradation from instream mining lowers the elevation of streamflow and the floodplain water table which in turn can eliminate water table-dependent woody vegetation in riparian areas, and decrease wet periods in riparian wetlands.
• The problem is serious in the case of the rivers in the southwest coast of India, especially in Kerala, where the rivers are small with limited river bed resources. At the same time, the mining of sand is on the rise to meet its ever increasing demand in the construction sector. 
• Guidelines on the extraction of sand say that the amount of sand removed should be in proportion to its replenishment rate and river width. Mining from a braided channel with a wide floodplain will have less impact than from a narrow channel. Manual mining is preferred over the use of machines but enforcement and monitoring of these guidelines remain weak. 
• A few states are exploring options like manufactured sand, produced by crushing of rocks and quarry stones, to meet the ever-increasing demand of the construction industry. The new sand mining framework suggests the use of geo-fencing, and GPS-enabled transportation to check illegal mining. Price control, the involvement of women self-help groups and regular audits of sand reserves have also been recommended. 

Conclusion

Sand sustains the rivers and the percolation of water to far off distances both for the growth of trees to sustain drinking water and raise cultivation. It is almost a lifeline to the human existence. The nation is to advance industrially and economically by the proper development and exploitation of these resources. It has to be remembered that the sand once removed cannot be replaced in the next generation as it takes centuries for replacement.