OR/14/068 Case study area

Lapworth, D J, Gopal, K, Rao, M S, and MacDonald, A M. 2014. Intensive groundwater exploitation in the Punjab — an evaluation of resource and quality trends. British Geological Survey Internal Report, OR/14/068.

Geography and climate

The Bist-Doab covers an area of 9060 km². The word “Doab” signifies the region between two rivers (here the Satluj and Beas). Groundwater levels are shallow in the confluence region with some associated salinity issues. Bist-Doab comprises the Nawanshahr, Hoshiarpur, Kapurthala and Jalandhar districts of Punjab State, India. It is bounded by Siwalik range in the north-east, the river Beas in the north and west sides and the river Satluj in south and east-south. The area lies between 30°51'N and 30"04'N latitude and 74"57'E and 76"40'E longitude (Figure 2). The study area is part of the Indo-Gangetic alluvial aquifer plain. The drainage density is high in the NE strip bordering the Siwalik hills, but it is moderate to low in the rest of the area with sub-parallel and sub-dendritic patterns. In the plain area the gradients are low, with a regional gradient of around 0.4 m/km towards the SE.

Figure 2 Location of Bist-Doab (ca.9000 km²) major drainage, canal network coverage and urban centres.

The Beas and Satluj rise in the high Himalayas and traverse long distances in the Himalayan and Siwalik zone before entering the state of Punjab. The Bist Doab area is comprised of a low hilly area locally known as the Kandi region, and the central plains. In the Kandi region, north-east portions of Hoshiapur and Nawanshehar, there are deeper groundwater tables, due to the change in topography, and this region is traditionally considered the recharge area for the deeper plain aquifer system. Some parts of Nawanshahr and Jalandhar districts are irrigated using canals from the Satluj, however, most of the area of Bist-Doab is irrigated using shallow groundwater (ca.90%). The ‘shallow’ boreholes abstract from aquifers that are normally at least 10 m thick and no deeper than 50 meters below ground level. ‘Deep’ boreholes abstract from aquifers that are for the most part >100 meters below ground level and are also >10 m thick.

The drainage density is high in the NE strip bordering the Siwalik hills, where there are regular parallel channels cutting through the Shiwalik range which drain on to the plain. Drainage density is moderate to low in the rest of the area with sub-parallel and sub-dendritic patterns. In the plain area the gradients are low, with a regional gradient of around 0.4 m/km towards the SE (Bowen, 1985).

The climate of the Bist-Doab is semi-arid and there is a moderate temperature and rainfall gradient SE–NW across the Bist-Doab region. There is annual average rainfall of ca.700 mm in Jalandhar, in the middle of the catchment, the greatest rainfall occurs between mid-June and September. Temperatures in the lower plain area range between 25–48°C in the summer (May) and between 5–19°C winter months. Slightly higher annual average rainfall occurs to the NE of the Bist-Doab region in the Shiwalik hills (ca.900 mm/a) where temperatures are also generally lower, however the seasonal variations in rainfall and temperature are similar to other parts of the Doab.

Geology

The Bist-Doab is part of the Indo-Gangetic alluvial aquifer plain. This is described in detail in Bowen (1985) and Khan (1984), and summarised below. Geomophologically the Bist-Doab can be divided into three zones, the Shiwalik and Kandi watershed, the interfluvial plain between the R Beas and the R Sutlej, and the floodplain areas. Thick deposits of Pleistocene to recent sediments derived from erosion of the Himalayas’ and lower lying foothills have formed the deep sedimentary alluvial plain aquifer we find today. The major lithologies and sequences in order of increasing age and depth comprise:

• Quaternary surface deposits
• Holocene Sirowal sediments and occasional gravels with inter-bedded course clastics from the Kandi belt and red clay beds to the southwest
• Pleistocene boulder beds and inter-bedded clays: Boulder conglomerate (Middle Pleistocene); Pinjore Psammite/Arenites with calcareous/ferruginous cements (late Pliocene)

Plate 1 Holocene Sirowal sedimentary deposits in the North of the catchment.

The polymictic nature of the sediments reveals their heterogeneous provenance resulting from an influx of sediment from a number of sources draining the Himalayas (Bowen, 1985). The sources are pre-Cenozoic and Palaeogene/Neogene or Cenozoic crystalline and sedimentary rocks in the vicinity of Shimla, identified through fragments of parent rock in the Pinjore beds. The infilling of the basin demonstrates that the rate of uplift and erosion was outstripped by the rate of deposition through the Holocene and Pleistocene. Fill, scour and bedding structures indicate a predominantly southward flow direction during this period (Bowen, 1985). Calcrete deposits, referred to in India as Kankar, are extensively developed within the sediments deposited in the Bist-Doab inter-fluvial area. This deposit is composed of calcium carbonate and has a nodular form in this region and is deposited as a result of upward capillary action in arid/semi-arid conditions and as a result of leaching minerals from shallow soil horizons. These can form low permeability horizons and are also important in controlling soil and groundwater pH and geochemical processes.

Hydrogeology

In the Kandi region, north-east portions of Hoshiapur and Nawanshehar, there are deeper groundwater levels, due to the change in topography, and this region is traditionally considered the recharge area for the deeper plain aquifer system. The transition from the Kandi belt to the plains and sudden change in slope results in a dense network of drainage that recharges the plain aquifers. Figure 3 shows a simple schematic cross-section with a regional conceptual model of groundwater flow and recharge processes. Zone 1 has higher rainfall (900 mm/y) and higher areal and surface water recharge, zone 2 has lower rainfall (700 mm/y) and recharge from irrigation and seepage from canals and zone 3 has lower rainfall (600 mm/y), shallow groundwater and limited recharge potential. Some parts of Nawanshahr and Jalandhar districts are irrigated using canals from the R Satluj, however, most of the area of Bist-Doab is irrigated using shallow (0–50 m) groundwater (>90% groundwater irrigation). Historically rising water levels, waterlogging and related salinity issues was a problem in the southwestern part of the Bist-Doab, and as the groundwater in this region is fresh groundwater pumping was encouraged to lower water tables and improve agricultural productivity.

The alluvial aquifer system comprises a series of layered aquifers of with higher porosity of sand and gravel deposits which are separated vertically by low permeability aquitards comprised of thick clay horizons as well thick Kankar deposits of CaCO₃. The aquifers and aquitards are highly variable both in terms of thickness and areal extent. Details from borehole logs in Bowen (1985) show that aquifers have horizons that are typically >20 m thick and are separated by clay and kankar horizons between 3–50 m thick. A N–S transect of logs in Bowen (1985) from Khudda (N) to Mioonwal (S) shows that aquifer and aquitard horizons are spatially highly variable. There are however regions of apparent continuity, although it must be noted that there are relatively few logs available, for example, between Njka (N) and Dhisian (S), covering a distance of ca.50 km, there appears to be a consistently thick (ca.15 m) clay horizon between the upper aquifer (<15 mbgl) and the second aquifer (ca.30–50 mbgl).

There is also clear evidence that paleochannels cut across low K horizons providing vertical connectivity and are important in controlling hydrogeolocial processes within the Indo-Gangetic plains (Samadder et al., 2011). This setting is considered comparable lithologically to locations further south in Gujurat reported by Phadtare (1985) and referred to by Rushton (1987). However, there is still limited evidence on the lateral extent of low K horizons and high K horizons or aquifers. Regionally, it is perhaps best described as an aquifer system which can be conceptualised as a series of aquifers with varying degrees of anisotropy but with overall higher horizontal (K_h) compared to vertical (K_v) hydraulic conductivity. The degree of anisotropy (K_h/K_v) can be as high as 10²–10⁴ in alluvial systems when significant clay layers are present (Michael and Voss, 2009; Sinha 2009). Early hydrogeological studies in this region focussed on understanding areal groundwater recharge using tritium tracers (Datta and Goel, 1977; Goel and Datta, 1977). Recharge studies carried out in at 7 sites across the Bist-Doab in 1972 (Datta and Goel, 1977) using tritium tagging gave average recharge (from irrigation and rainfall) values of 93 ± 60 mm for the monsoon period between June and November. The data set showed a bimodal distribution with one cluster of sites with average recharge values of 35 ± 3 mm and a second cluster with much higher average recharge of 136 ± 35 mm, with low recharge values located close to floodplain regions and the higher values in the plains region.

There is limited aquifer property data for transmissivity (T) and storage coefficients (S) in the study area, a summary of values are presented in Bowen (1985). However, there is a paucity of data and so estimates of T and S must be treated with caution, quoted values for transmissivity range from 1700–5180 m²d^-1 from shallow aquifers across the catchment. Storage coefficients in the Kandi and Shiwaliks range from 0.0013–0.004 and from the plain region higher values have been estimated between 0.082–0.31.

Although it is beyond the scope of this report, the quarterly long-term water level monitoring data could be used to estimate the spatial variation of recharge, provided certain assumptions regarding the effects of abstraction (and storage) on water levels hold true. Our high frequency monitoring data collected at 6 sites shall be critical in validating the applicability of this technique with low frequency data.

Figure 3 Simplified schematic cross section of post monsoon regional groundwater flow (distance from the edge of the Shiwalik range to Bussowal is ca.100 km).

Groundwater quality issues from previous studies

In Ludhiana, to the south of Bist-Doab, the shallow aquifer is contaminated with cyanide and chromium from industrial waste sources (Singh, 1982). More recent studies have largely focussed on groundwater quality assessments for irrigation (Kuldip-singh et al., 2013; Kuldip-Singh et al., 2011; Purushothaman et al., 2012) and used GIS approaches to map the potential of artificial recharge in the area to augment natural recharge (Singh et al., 2013 ; Singh et al., 2010). Dhillon and Dhillon (2003) investigated the links between elevated soil selenium (Se) concentrations and Se occurrence in shallow groundwaters in part of the Bist-Doab region. Future climate change scenarios point to an increases in high intensity rainfall during monsoon months, but overall lower soil moisture in NW India, increasing the potential for microbial contamination of shallow groundwaters (Nicholls et al., 2012; Parry et al., 2007). Lower soil moisture levels may also reduce the potential for soil denitrification and therefore a greater potential for nitrate leaching to groundwater (Groffman and Tiedje, 1989; Ruser et al., 2006).