Intensive groundwater exploitation in the Punjab : an evaluation of resource and quality trends

This report summarises initial findings from a case study investigating the response of groundwater resources in Punjab State, India, to irrigated agriculture. Punjab was central to India’s green revolution, and with fertile soils, abundant surface water and groundwater resources, Indian’s farmers soon transformed the State to be the “bread basket” of India. Currently approximately 20% and 11% respectively of India’s wheat and rice production, 10% of cotton production comes from Punjab. The aim of the case study is to examine the response of groundwater in a representative area within Punjab to current pressures from sustained intensive abstraction and pollution, investigate groundwater recharge, and forecast likely future trajectories. The Bist-Doab area was chosen as for the case study: the geology and hydrogeology is typical of the Punjab, situated on the thick and extensive multi-layered alluvial Indo-Gangetic aquifer and has an annual average rainfall of 700 mm. The Doab is one of the most productive agricultural regions in the Punjab and has experienced intense groundwater pumping from shallow aquifers for at least the last four decades. The hydrogeology of this region is best understood as an aquifer system comprising a series of thick high permeability horizons (>10 m thick) divided by thick low permeability horizons with highly variable lateral extent. Locally these are referred to as the first (shallow), second and third etc. (deep) aquifers, although the aquifers are not laterally continuous over long distrances. The following work was undertaken from 2013 to 2014: An analysis of groundwater level monitoring data (1970-2012) from the Indian Central Ground Water Board (CGWB) was carried out. New hydrochemical observations and residence time indicators (CFC and SF6) taken from 19 locations were obtained from paired shallow (100 mbgl) sites across the Bist-Doab under pre and post monsoon conditions. Stable isotope observations were collected and assessed within the context of an ongoing study by NIH investigating spatial and temporal changes in stable isotope chemistry in groundwater and surface water across Bist-Doab. Long-term groundwater monitoring undertaken by the CGWB since the 1970s shows declining shallow pre-monsoon groundwater levels (up to 0.8 m/y in places) across 20-25% of the Bist-Doab. Hydrographs responses imply that for some areas this has led to enhanced recharge during the monsoon. However, for the most affected region of the Bist-Doab, declining post monsoon water levels suggest that abstraction for irrigation is now outstripping the enhanced recharge potential. In the long-term this will lead to a continued decline in shallow groundwater levels pre-monsoon, currently commonly found to be >20 mbgl, with future implications for irrigation. For most sites there is a significant difference between stable isotope values for the paired deep and the shallow groundwater, with deeper sites showing isotopically depleted signatures relative to the shallow samples. This is consistent with different recharge areas and pathways for the paired sites at any given location, with the deeper sites have a greater component of water that was recharged some distance up-gradient (i.e. towards the recharge zone at the foot of the Shiwalik range). This source has a depleted isotope signature compared to the shallow aquifer due to Raleigh distillation processes as monsoon moisture tracks from the Bay of Bengal. Based on the distinct depleted stable isotope values of the Sutlej canal system, there is no evidence of significant component of regional groundwater recharge in either the shallow or deeper aquifer from this source. However, it is likely that this is important at locations in close proximity to the canal network. Results obtained using chlorofluorocarbon (CFC-12) groundwater age tracers show that average shallow groundwater mean residence times (MRTs) are 29 years and 30 years under post-monsoon and pre-monsoon conditions. Deep groundwater (>100 mbgl) had median MRTs of 45 vii years. There is no obvious relationship between deep groundwater MRTs and distance from the recharge zone at the foot of the Shiwalik hills. However, deep groundwater MRTs are much younger than would be expected under natural groundwater flow regimes, where groundwater residence times of the order of ca.102-103 years or more might be expected based on the aquifer properties and the distance from the recharge zone, some 50- 100 km down-gradient in many cases. Areas with fastest long-term declining groundwater levels show evidence of enhanced modern recharge in both shallow and deep groundwater, suggesting that there is a significant component of vertical leakage to deeper aquifers induced by long-term intensive pumping. This corroborates findings from modelling studies undertaken in analogous multi-layered alluvial systems in Gujerat, India (Rushton 1986). There is evidence of nitrate breakthrough from the shallow groundwater to depth and this is likely to be enhanced in the future if the current increases in pumping from the shallow and deep aquifers continue. This has implications for future contamination of deep sources of drinking water from other anthropogenic contaminants such as pesticides. The naturally occurring contaminants arsenic and fluoride were present at concentrations below WHO guideline drinking water limits for all sites and median concentrations were below 2 g/L and 0.4 mg/L respectively. Uranium concentrations in deep groundwater are significantly higher compared to shallow groundwater (p15 g/L, the provisional WHO guideline concentration for drinking water is currently 30 g/L (WHO, 2012). This is a result of water-rock interactions and mineral dissolution and longer residence times. The findings from this case study have broad relevance across a large geographical area as similar groundwater typologies extend within the Indus basin, to the west across Indian Punjab, Rajasthan and Pakisan Punjab as well as in the Ganga basin to the east in the Indian states of Haryana and Delhi. While the broad findings from this study are relevant across a large geographical area, local anthropogenic and geogenic factors, as well as heterogeneity, will of course influence the recharge, hydraulic flow processes and geochemistry, and need to be considered in a consistent way

Basic and ultrabasic volcanic rocks from the Argyll Group (Dalradian) of NE Scotland

The Dalradian Supergroup of the Scottish Highlands is a largely metasedimentary succession of Neoproterozoic to Early Cambrian age, metamorphosed during the Caledonian Orogeny. The rocks were deposited on the Laurentian margin during and following the break-up of Rodinia. This rift setting is evidenced, in the upper half of the succession, by the presence of several volcanic sequences. A significant development of these volcanic rocks occurs in the NE Grampian Highlands. There, the Blackwater Formation, within the Argyll Group of the Huntly area, is dominated by basic and ultrabasic metavolcanic rocks, with intercalated metasedimentary rocks. The rocks were metamorphosed in the amphibolite facies, with the Mg contents of their dominant amphiboles apparently reflecting those of the whole-rock protoliths. The protoliths ranged from ultrabasic picritic types (MgO up to 35 wt%) through high-magnesia basalts to basaltic andesites and andesites. The magmas feeding the volcanism were of tholeiitic affinity, broadly similar to metavolcanic rocks elsewhere in the Dalradian. Higher-Nb and lower-Nb groups can be distinguished. The inferred parental magmas were basalts with MgO c. 10 wt%. The ultrabasic rocks formed by accumulation of olivine and minor Cr-spinel within the parental basalts. Some more evolved rocks show evidence of minor (5–10 wt%) accumulation of Fe–Ti oxides. Primary magmas of the Blackwater metavolcanic rocks were generated from a mantle source, or sources, relatively enriched compared to the MORB source. It is speculated that all the Dalradian metavolcanic rocks represent varying degrees of mixing of magmas from this source and a depleted, MORB-like, mantle source

Threats to groundwater supplies from contamination in Sierra Leone, with special reference to Ebola care facilities

The outbreak of Ebola virus disease in West Africa in 2014 is the worst single outbreak recorded, and has resulted in more fatalities than all previous outbreaks combined. This outbreak has resulted in a large humanitarian effort to build new health care facilities, with associated water supplies. Although Ebola is not a water-borne disease, care facilities for Ebola patients may become sources of outbreaks of other, water-borne, diseases spread through shallow groundwater from hazard sources such as open defecation, latrines, waste dumps and burial sites to water supplies. The focus of this rapid desk study is to assess from existing literature the evidence for sub-surface transport of pathogens in the context of the hydrogeological and socio-economic environment of Sierra Leone. In particular, the outputs are to advise on the robustness of the evidence for an effective single minimum distance for lateral spacing between hazard sources and water supply, and provide recommendations for protecting water supplies for care facilities as well as other private and public water supplies in this region. Preliminary conclusions were: Considering the climate (heavy intense rainfall for 8 months), the hydrogeological conditions (prevalent shallow and rapidly fluctuating water tables, permeable tropical soils), the pervasive and widespread sources of hazards (very low improved sanitation coverage), and the widespread use of highly vulnerable water points there is little evidence that simply using an arbitrary lateral spacing between hazard sources and water point of 30 – 50 m would provide effective protection for groundwater points. An alternative framework that considers vertical as well as lateral separation and the integrity of the construction and casing of the deeper water points is recommended to protect water supplies from contamination by pathogens. The shallow aquifer, accessed by wells and springs, must be treated as highly vulnerable to pollution, both from diffuse sources and from localised sources. Diffuse pollution of groundwater from surface-deposited wastes including human excreta is likely to be at least as important as pollution from pit latrines and other point sources, given the low sanitation coverage in Sierra Leone. Even though conditions are not optimal for pathogen survival (e.g. temperatures of >25° C), given the very highly permeable shallow tropical soil zone, and the high potential surface and subsurface loading of pathogens, it is likely that shallow water sources are at risk from pathogen pollution, particularly during periods of intense rainfall and high water table conditions. Extending improved sanitation must be a high priority, in conjunction with improved vertical separation between hazard sources and water points, in order to reduce environmental contamination and provide a basis for improved public health. We recommend that risk assessments of water points are undertaken for health care facilities as soon as possible including: detailed sanitary inspections of water points within the 30 – 50 m radius suggested by the Ministry of Water Resource; assessments of the construction and integrity of the water points; a wider survey of contaminant load and rapid surface / sub surface transit routes within a wider 200 m radius of water points. Analysis of key water quality parameters and monitoring of water levels should be undertaken at each water point in parallel with the risk assessments. The translation of policy on water, sanitation and hygiene into implementation needs complementary research to understand key hydrogeological processes as well as barriers and failings of current practice for reducing contamination in water points. A baseline assessment of water quality status and sanitary risks for e.g. wells vs boreholes, improved vs unimproved sources in Sierra Leone is needed. Understanding the role of the tropical soil zone in the rapid migration of pollutants in the shallow subsurface, i.e. tracing rapid pathways, and quantifying residence times of shallow and deep groundwater systems are key knowledge gaps

Modal stability of inclined cables subjected to vertical support excitation

In this paper the out-of-plane dynamic stability of inclined cables subjected to in-plane vertical support excitation is investigated. We compute stability boundaries for the out-of-plane modes using rescaling and averaging methods. Our study focuses on the 2:1 internal resonance phenomenon between modes that occurs when the excitation frequency is twice the first out-of-plane natural frequency of the cable. The second in-plane mode is excited directly, while the out-of-plane modes can be excited parametrically. An analytical model is developed in order to study the stability regions in parameter space. In this model we include nonlinear coupling effects with other modes, which have thus far been omitted from previous models of parametric excitation of inclined cables. Our study reflects the importance of such effects. Unstable parameter regions are defined for the selected cable configuration. The validity of the proposed stability model was tested experimentally using a small-scale cable actuator rig. A comparison between experimental and analytical results is presented in which very good agreement with model predictions was obtained. r 2008 Elsevier Ltd. All rights reserved

Nitrogen sources, transport and processing in peri-urban floodplains

Peri-urban floodplains are an important interface between developed land and the aquatic environment and may act as a source or sink for contaminants moving from urban areas towards surface water courses. With increasing pressure from urban development the functioning of floodplains is coming under greater scrutiny. A number of peri-urban sites have been found to be populated with legacy landfills which could potentially cause pollution of adjacent river bodies. Here, a peri-urban floodplain adjoining the city of Oxford, UK, with the River Thames has been investigated over a period of three years through repeated sampling of groundwaters from existing and specially constructed piezometers. A nearby landfill has been found to have imprinted a strong signal on the groundwater with particularly high concentrations of ammonium and generally low concentrations of nitrate and dissolved oxygen. An intensive study of nitrogen dynamics through the use of N-species chemistry, nitrogen isotopes and dissolved nitrous oxide reveals that there is little or no denitrification in the majority of the main landfill plume, and neither is the ammonium significantly retarded by sorption to the aquifer sediments. A simple model has determined the flux of total nitrogen and ammonium from the landfill, through the floodplain and into the river. Over an 8 km reach of the river, which has a number of other legacy landfills, it is estimated that 27.5 tonnes of ammonium may be delivered to the river annually. Although this is a relatively small contribution to the total river nitrogen, it may represent up to 15% of the ammonium loading at the study site and over the length of the reach could increase in-stream concentrations by nearly 40%. Catchment management plans that encompass floodplains in the peri-urban environment need to take into account the likely risk to groundwater and surface water quality that these environments pose

Two-Dimensional Vortex Lattice Melting

We report on a Monte-Carlo study of two-dimensional Ginzburg-Landau superconductors in a magnetic field which finds clear evidence for a first-order phase transition characterized by broken translational symmetry of the superfluid density. A key aspect of our study is the introduction of a quantity proportional to the Fourier transform of the superfluid density which can be sampled efficiently in Landau gauge Monte-Carlo simulations and which satisfies a useful sum rule. We estimate the latent heat per vortex of the melting transition to be $\sim 0.38 k_B T_M$ where $T_M$ is the melting temperature.Comment: 10 pages (4 figures available on request), RevTex 3.0, IUCM93-00

Comparative performance of rural water supplies during drought

As rural African communities experience more frequent and extreme droughts, it is increasingly important that water supplies are climate resilient. Using a unique temporal dataset we explore rural water supply (n = 5196) performance during the 2015–16 drought in Ethiopia. Mean functionality ranged from 60% for motorised boreholes to 75% for hand-pumped boreholes. Real-time monitoring and responsive operation and maintenance led to rapid increases in functionality of hand-pumped and, to a lesser extent, motorised boreholes. Increased demand was placed on motorised boreholes in lowland areas as springs, hand-dug-wells and open sources failed. Most users travelled >1 h to access motorised boreholes but 30 m) groundwater performed best during the drought. Prioritising access to groundwater via multiple improved sources and a portfolio of technologies, such as hand-pumped and motorised boreholes, supported by responsive and proactive operation and maintenance, increases rural water supply resilience

Groundwater, flooding and hydrological functioning in the Findhorn floodplain, Scotland

A large floodplain of the River Findhorn, northeast Scotland, was investigated using hydrogeological and hydrochemical methods (including residence time indicators) to characterise groundwater/surface-water coupling and groundwater flooding. The study demonstrated widespread stratification within the floodplain: shallow (30 mm). Persistent groundwater flooding occurs within topographical lows and also in the discharge zone where it is largely managed with a series of drains constructed in the 19th century. The significant and complex role of groundwater in floodplains, demonstrated by this study, highlights the importance of fully considering groundwater in flood management schemes