Recharge processes: piston flow vs preferential flow in semi-arid aquifers of India

• Published in: Hydrogeology journal Vol. 11; no. 3; pp. 387 - 395
• Main Authors: Sukhija, B S, Reddy, D V, Nagabhushanam, P, Hussain, S
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer Nature B.V 01.06.2003
• Subjects: Aquifers; Geochemistry; Geology; Granite; Groundwater; Groundwater discharge; Groundwater flow; Hydrology; Pistons; Sandstones; Tracers; Tritium; India
• ISSN: 1431-2174; 1435-0157
• DOI: 10.1007/s10040-002-0243-3

Study of groundwater recharge processes is vital for quantification of total natural recharge to the aquifers. One of the recharge processes demonstrated earlier by tracer experiments in the unsaturated zone is that of piston flow movement of soil moisture. Based on this recharge process, environmental tritium, chloride and injected tritium studies have been carried out extensively in various geological environs of India. The purpose of this paper is to evaluate the validity of the piston flow concept in different geological environs viz. consolidated fractured and weathered granites, semi-consolidated sandstones and unconsolidated alluvial tracts, and quantify the contribution from this process as well as that from the preferential flow mechanism using different tracers. Analysis of tracer data demonstrates that the preferential flow recharge process contributes very significantly (an average of 75% of total recharge) in the case of fractured granites and is important (an average of 33% of total recharge) for semi-consolidated sandstones, whereas the preferential flow recharge component is minimal in unconsolidated alluvial tracts (piston flow model is applicable). These findings necessitate re-evaluation of the total natural recharge potential of the above mentioned geological environs in view of the significant preferential flow recharge that is evidenced and estimated.