The pressure of population and growing economy has lead to a construction boom in India. Hectare after hectare of land, irrespective of its use is being cleared to make room for towering apartments for the sea of humanity. It is common knowledge that sand is one of the main ingredients of the construction material. The towering apartments are in a way towers of sand.
From where does this sand come? Major source of this sand are the rivers. However, in the Deccan country of India the weathering and erosion of granitic terrain produces coarse sand which is a common building material. Compared to the rivers of the north, the rivers of Deccan are able to erode less, because of the hard rock terrain. Therefore the sand available from these rivers is proving to be less to cope up with the demand of sand for the hectic construction activity at Bangalore.
So much is the demand for sand that enterprising farmers have resorted to excavating sand from their fields to earn a quick buck, report Rajendra Hegde, and his co-workers from the National Bureau of Soil Survey and Land Use Planning, Regional Centre, Hebbal, Bangalore in July 2008 issue of Current Science.
Problem with a terrain like Karnataka is that agriculture depends on the thin soil cover, which is a product of erosion of the rocky substrate. This weathered granite, locally termed 'Chettu' is a source of soil for agriculture and also acts as a ground water reservoir. Naturally land for agriculture is limited. Sudden spurt of construction activity at Bangalore has turned the development of the state to more on urban-centric lines. Consequently there is a migration of population from villages to urban centre. The infrastructure at urban centre is under great pressure and demands for more shelters, office buildings, shopping centers, hospitals etc is on the increase.
The brunt of the demand is faced by the riverbeds. They are being over exploited reports Hegde. This leads to reduction in capacity of the rivers to hold water. Simultaneously the sand cover on the ground which acts as an aquifer leads to reduction in the volume of water holding area and causes rapid evaporation of groundwater. Brick manufacturing on the outskirts of Bangalore compounds the problem. Degraded soils take 1000 years to regenerate.
How hectic is the construction activity can be gauged from the fact that nearly 4000 truck loads of sand per day arrives in Bangalore to meet the demand. Hegde estimates that while 75% of the demand is met by the sand extracted from the river bed and remaining 25% comes from the tank beds, agricultural fields and village common lands. Sand recovered from the topsoil is actually not true sand but sand like material. It is mixed with river sand to meet the enormous demand. Incidentally this is a recent development, since past 3-4 years.
A somewhat similar scenario was found by this author in Tamilnadu, where tanker loads of drinking water was being imported to urban areas like Chennai in 2005 from agriculture fields in a radius of 30 km. Once the tube-well dried due to overexploitation, the enterprising farmers were extracting even the sand from the borehole. This subsurface mining of sand caused many a ground collapses too. It was found that each tube-well owner was earning about Rs15000 per month, without tilling centimeter of soil. Likewise the study of Hegde says that sand extraction is providing reasonably gainful employment for many farmers and landless laborers in the region.
The sand extraction from the soil of agricultural lands in Karnataka has yet another serious dimension. In order to extract, top soil containing the soil organic matter (SOM) has to be removed. SOM is a multipurpose matter-it makes the soil fertile, enhances the water holding capacity of the soil and resists erosion and run off of water. Fields with rich soils do not develop a crust even in severest droughts. SOM provides the required porosity to the soil and makes tilling of the fields easier.
Top soils deprived of SOM affect the soil profile at depth. The rate of production of microbial population is affected which in turn affects the nutrient availability to the plants. Soils deprived of SOM reduce the hydraulic conductivity and ultimately the plant population and growth get adversely affected, leading to crop losses.
A scientific study can not be conclusive unless proved by scientific facts gathered from the area, In order to carry out a systematic ecological study and socio-economic implications of sand extraction from surface soils, Hegde and his team studied 15 such units active in five villages situated in Bangalore Rural district.
It was found that lot of water is used by the sand extractors for washing the soil and recovering sands. Nearly 132000 liters of water is required to produce one truck load of sand. Hegde and his team estimate that approximately 21900 lakh gallons of water is annually consumed to produce the sand for the sky-scrappers of Bangalore. This water is pumped from deep bore-wells in the area, thereby reducing the groundwater level of a water deficient area, presently reeling under drought conditions. Excessive drawl of ground water has led to drying of all the dug wells around Bangalore.
The sand extractor makes a profit of Rs. 2100 per truck load of sand. Since water has to be pumped for the job with the help of diesel operated pumps nearly 3000 liters of diesel is consumed for this business alone around Bangalore everyday.
As it happens always the poor farmers can not reap the benefits of sand extraction business because of the overhead costs of labour, soil, water, diesel etc. It is estimated that the enterprise generates turnover of Rs. 146 crores per annum in the region and also an employment of 33 lakh man-days, out of which 75% is on the farm itself. Income generated for laborers by this source are to the tune of Rs 71 crores/annum says Hegde.
Bangalore area has been facing drought like conditions for the past 6-7 years. Despite dwindling farm income, the cases of farmer's suicide are unheard of in this period from the area. It is mainly because the farmers are able to sustain by working as labor for the sand extracting contractors.
One might ponder and ask if sand extraction is providing a livelihood to the poor farmers, then where is the problem. Well the problem is ecological, not social. Extraction of sand is increasing the finer content that is, silt in the soil. Thereby not only the arability of the soil is reduced, even the recharge of groundwater is affected. Silt being impervious, forms a kind of a pan and lets the water run off. Thus wash water coming out of the sand producing 'factories' is not safe for the village tanks or for agricultural use.
Study by Hegde and his colleagues shows that for producing one truck load of sand nearly 120 cubic meter topsoil is used. Thus in a year nearly 43.8 million cubic meters of soil is extracted and soil from 18600 hectare land is lost every year. Farms minus the topsoil are redundant for agriculture. Hedge suggests soil reclamation to use the left over silty soil for agriculture. However, the fact remains that once the topsoil is removed, nature takes 1000 years to regenerate it. Whether the towers of sand- those skyscrapers called apartments in Bangalore will remain for 1000 years to see the green fields again or not, only time will tell. But a fact which every Bangalorean must realize is that he is going to have parched throats or else will have to import drinking water.
One can have either the sandy castles or the sands of time. One can not afford both in such a situation.