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IMPORTANCE OF SAND AND ILL CONSEQUENCES OF EXCESSIVE SAND MINING
Jul 30, 2014

The spectacular growth of the construction industry has had unintended consequences for every river in India today. The mining of sand — which is an essential part of construction — has often been in the news, largely due to the control of local mafias over this minor mineral. Most people also intuitively recognise that sand-mining has damaged, and continues to damage, the delicate ecosystem of India’s rivers, on which millions of people depend for their drinking and household needs, livelihoods and irrigation. Yet, what is little understood is this: why is sand necessary for the river, and what role does it play?

Excessive instream sand-and-gravel mining causes the degradation of rivers. Instream mining lowers the stream bottom, which may lead to bank erosion. 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 system.


Excessive instream sand mining is a threat to bridges, river banks and nearby structures. Sand mining also affects the adjoining groundwater system and the uses that local people make of the river. 


Instream sand mining results in the destruction of aquatic and riparian habitat through large changes in the channel morphology. Impacts include bed degradation, bed coarsening, lowered water tables near the streambed, and channel instability. These physical impacts cause degradation of riparian and aquatic biota and may lead to the undermining of bridges and other structures. Continued extraction may also cause the entire streambed to degrade to the depth of excavation. 


Sand mining generates extra vehicle traffic, which negatively impairs the environment. Where access roads cross riparian areas, the local environment may be impacted.


Impact on river and groundwater :


Sand, simply, is the soil of the river, providing and sustaining virtually all life that exists in the river itself. Along with another very important mineral, gravel, it forms part of the hyporheic zone, an intermediate zone between the surface water of the river and the groundwater beneath.


The hyporheic zone has been studied extensively all over the world for the last seventy years and it is now well accepted that this zone performs critical functions, each necessary for the long-term survival of a river. Recharging the ground water table far beyond the river basin itself by slowing down the flow of water in the river and allowing for percolation, not just downwards but laterally across large areas on either side of the river as well — exactly how large an area is recharged by the river depends on various factors, including nature of the soil, the topography and so on. Indeed, a study in the United States showed that where the hyporheic zone was minimal, water recharge was limited and wells often went dry in summer.


Impact on Riparian Habitat, Flora and Fauna :


Instream mining can have other costly effects beyond the immediate mine sites. Many hectares of fertile streamside land are lost annually, as well as valuable timber resources and wildlife habitats in the riparian areas. Degraded stream habitats result in lost of fisheries productivity, biodiversity, and recreational potential. Severely degraded channels may lower land and aesthetic values.


All species require specific habitat conditions to ensure long-term survival. Native species in streams are uniquely adapted to the habitat conditions that existed before humans began large-scale alterations. These have caused major habitat disruptions that favored some species over others and caused overall declines in biological diversity and productivity. In most streams and rivers, habitat quality is strongly linked to the stability of channel bed and banks. Unstable stream channels are inhospitable to most aquatic species.


Factors that increase or decrease sediment supply often destabilize bed and banks and result in dramatic channel readjustments. For example, human activities that accelerate stream bank erosion, such as riparian forest clearing or instream mining, cause stream banks to become net sources of sediment that often have severe consequences for aquatic species. Anthropogenic activities that artificially lower stream bed elevation cause bed instabilities that result in a net release of sediment in the local vicinity. Unstable sediments simplify and, therefore, degrade stream habitats for many aquatic species. Few species benefit from these effects.


The most important effects of instream sand mining on aquatic habitats are bed degradation and sedimentation, which can have substantial negative effects on aquatic life. The stability of sand-bed and gravel-bed streams depends on a delicate balance between streamflow, sediment supplied from the watershed, and channel form. Mining-induced changes in sediment supply and channel form disrupt channel and habitat development processes. Furthermore, movement of unstable substrates results in downstream sedimentation of habitats. The affected distance depends on the intensity of mining, particles sizes, stream flows, and channel morphology.The complete removal of vegetation and destruction of the soil profile destroys habitat both above and below the ground as well as within the aquatic ecosystem, resulting in the reduction in faunal populations.


Channel widening causes shallowing of the streambed, producing braided flow or subsurface intergravel flow in riffle areas, hindering movement of fishes between pools. Channel reaches become more uniformly shallow as deep pools fill with gravel and other sediments, reducing habitat complexity, riffle-pool structure, and numbers of large predatory fishes.Sand is a refuge for fish and an incubator for eggs. While lakhs of fishermen are critically dependant on fishing, fish itself is a vital source of rural protein and, as is now being studied, the humungous scale of sand and gravel extraction (along with the number of hydel projects coming up) is impacting fish availability all across. Ironically, many fishermen, in an effort to keep their incomes from falling, are part of the extensive sand mining network, working the river-beds for a fraction of the amount the sand is sold to end-users. Sand served the function of buffering agricultural lands and towns from rising water levels during floods as by its very nature it is porous. To understand this better, one only needs to fill a glass with sand and pour water into it! This value of sand — that of being a vast storage tank of clean water — has an additional property: during the dry months, sand releases some of this water to keep the river flowing, ensuring (sand-filtered) water for our needs.


Harbouring unique invertebrate fauna and micro-organisms such as fungi and microbes that filter the water, due to its physical, chemical and biological conditions. The sediment particles, for instance, impede the flow of silt and particulate matter as water enters and moves through sand. A second, biological filtering mechanism works in a manner similar to the trickle filters of sewage treatment plants, where nutrients dissolved in river water are taken up or transformed by microbial bio-films coating the sediments, into food for the many species of invertebrates that live in the hyporheic zone. The chemical conditions prevalent within the hyporheic zone allow the precipitation of dissolved minerals and metals, which is then trapped by the physical filter, where it may be degraded biologically. These are complex processes, evolved over thousands of years, and the removal of the sand-and-gravel layer of the river ecosystem is inhibiting the self-cleaning mechanism of the river, even as India’s rivers receive increasing loads of toxic and sewage wastes from urban and agricultural areas. The removal of sand and the increasing pollution are irreversibly damaging the ecology of all rivers in India.


Stability of Structures is Affected :


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.


Several studies have documented the bed degradation caused by the two general forms of instream mining: (1) pit excavation and (2) bar skimming. Bed degradation, also known as channel incision, occurs through two primary processes: (1) headcutting, and (2)"hungry" water. In headcutting, excavation of a mining pit in the active channel lowers the stream bed, creating a nick point that locally steepens channel slope and increases flow energy. During high flows, a nick point becomes a location of bed erosion that gradually moves upstream Headcutting mobilizes substantial quantities of streambed sediments which are then transported downstream to deposit in the excavated area and locations further downstream. In gravel-rich streams, effects downstream of mining sites may be short-lived when mining ends, because the balance between sediment input and transport at a site can reestablish itself relatively quickly. Effects in gravel-poor streams may develop rapidly and persist for many years after mining has finished. Regardless of downstream effects, headcutting in both gravel-rich and gravel-poor streams remains a major concern. Headcuts often move long distances upstream and into tributaries, in some watersheds moving as far as the headwaters or until halted by geologic controls or man-made structures. 


A second form of bed degradation occurs when mineral extraction increases the flow capacity of the channel. A pit excavation locally increases flow depth and a barskimming operation increases flow width. Both conditions produce slower streamflow velocities and lower flow energies, causing sediments arriving from upstream to deposit at the mining site. As streamflow moves beyond the site and flow energies increase in response to the "normal" channel form downstream, the amount of transported sediment leaving the site is now less than the sediment carrying capacity of the flow. This sediment-deficient flow or "hungry" water picks up more sediment from the stream reach below the mining site, furthering the bed degradation process 


Summary :


Impacts of sand mining can be broadly clasified into three categories:

  • Physical : The large-scale extraction of streambed materials, mining and dredging below the existing streambed, and the alteration of channel-bed form and shape leads to several impacts such as erosion of channel bed and banks, increase in channel slope, and change in channel morphology. These impacts may cause: (1) the undercutting and collapse of river banks, (2) the loss of adjacent land and/or structures, (3) upstream erosion as a result of an increase in channel slope and changes in flow velocity, and (4) downstream erosion due to increased carrying capacity of the stream, downstream changes in patterns of deposition, and changes in channel bed and habitat type.

  • Water Quality : Mining and dredging activities, poorly planned stockpiling and uncontrolled dumping of overburden, and chemical/fuel spills will cause reduced water quality for downstream users, increased cost for downstream water treatment plants and poisoning of aquatic life.

  • Ecological : 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.

What is needed is a national effort to develop an ecologically safe, cost-effective, technically comparable substitute for sand and to critically evaluate the impact on the hyporheic zone prior to the clearance of a hydroelectric project. To ensure water security for India’s future, we need to keep sand where it belongs — in the river.

NATIONAL GREEN TRIBUNAL  RULING :

Earlier, The National Green Tribunal (NGT) issued a restraint order against all sand mining activity being carried out across the country without environmental clearance. The order was passed in the light of the controversy surrounding the suspension of IAS officer posted as sub divisional magistrate (SDM) in Greater Noida in Gautam Buddh Nagar in Uttar Pradesh after she cracked down on the mining mafia. While passing the order, NGT reaffirmed the Supreme Court’s order last year which banned any kind of mining of minor minerals, including sand, without environmental clearance from the Union Ministry of Environment and Forests. The  bench said that removal of minerals from river beds is posing a serious threat to the flow of rivers, survival of forests upon river banks and most seriously to the environment of river banks, especially those of the Yamuna, Ganga, Chambal, Gaumti and Revati rivers.


The NGT bench observed that “majority of persons carrying out mining activity of removing mineral from the river bed have no licence to extract sand; they also have not obtained clearance from MoEF/SEIAA at any stage in terms of the Environment (Protection) Act, 1986  (EP Act, 1986) as well as Air (Prevention and Control of  Pollution) Act, 1981 and Water (Prevention and Control of Pollution) act, 1974.”For these reasons the bench ordered that it restrains any person, company, authority to carry out any mining activity or removal of sand, from river beds anywhere in the country without obtaining Environmental Clearance from Ministry of Environment Forests/SEIAA and licence from the competent authorities.

 

 


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