Groundwater occurs in semi-confined to confined conditions in the porous alluvial formations. Gravel, coarse to fine sands, clays and silty clay constitute the alluvial material and, of these, the gravel and sand form potential aquifers
Granular zones are limited in many places in Chennai city and the shallow wells tapping only alluvium dry up in summer
Groundwater is recharged in aquifers naturally by rain and to a smaller extent by surface water (rivers and lakes)
Water first collecting in lakes, ponds, tanks — all very efficient recharge structures
Recharge can be impeded by human activities including paving, development, building on lakes and marsh areas, and blocking access for rainwater to flow into existing tanks and lakes
In Chennai, 39K seek duplicate certificates
In Chennai district alone, 39,181 persons, to date, have applied for obtaining duplicates of documents such as educational certificates, land deeds, ration cards etc. that were lost in the recent floods. On December 23 alone, 3,640 applications were received through special camps, that have been held since December 14 in the 10 taluks of Chennai district. Acknowledgement receipts have been issued to the applicants. The number of applications received in each department on Wednesday are: Revenue (104), School Education (773), Registration (181), Transport (828), Food and Civil Supplies (172), Chennai Corporation (976), Census (211), Public Sector banks (249), Public Sector Undertakings (118), Differently-abled (21) and Labour and Employment (7). People can also approach service centres for duplicates of documents.