OR/14/069 Summary and conclusions

Bricker, S H, Yadav, S K, MacDonald, A M, Satyal, Y, Dixit, A, and Bell, R. 2014. Groundwater resilience Nepal: preliminary findings from a case study in the Middle Hills. British Geological Survey Internal Report, OR/14/069.

Groundwater resources in the Middle Hills of Nepal perform a major role in supplying domestic and irrigation water and in regulating river flows. However, there has been little systematic study of groundwater within the Middle Hills, making it difficult to evaluate how water supplies and river flows may change in response to climatic and anthropogenic change. To begin to build an evidence base, two catchments in the middle hills were investigated to: characterise the hydrogeology of the catchments and wider hydrogeological setting; assess water supplies and water usage; and evaluate how resilient groundwater may be to change.

Field work

Two contrasting sub-catchments within the Kali Gandaki river catchment were investigated.

The first lies within Ramche VDC in Myagdi district and encompasses the villages of Ramche and Nangi. Ramche catchment lies at elevations of 1200 m to more than 3000 m with a sub- tropical to alpine climate. Land cover within the catchment is predominantly community forest, with terraced agriculture–agriculture is the primary source of income. Households are entirely reliant on springs for their water supply, some of which are captured upslope and supplied to the village, and others within the village where water is collected at the source.

The second catchment lies within Madanpokhara VDC in Palpa district. Madanpokhara catchment lies at elevations of less than 1000 m with a tropical to sub-tropical climate. Land cover in the catchment is dominated by agriculture, with little terracing, and there is some community forest on the hillslopes. Communities in Madanpokhara use a combination of springs and shallow tubewells to meet their water requirements. Madanpokhara is a drier catchment and entirely reliant on monsoon rain.

Fieldwork was undertaken during the post-monsoon season (16th–26th September 2013) and pre-monsoon season (23rd April–7th May 2014). Thirty-one sites across the two catchments were investigated using a combination of water supply surveys, spring flow and temperature measurements, and sampling for inorganic chemistry, stable isotope and groundwater residence time and noble gas indicators. In addition 12 months of weekly hydrological monitoring and monthly water usage surveys were undertaken at seven springs.

Preliminary findings

Based on the observations from the two field visits and a preliminary interpretation of the data some initial findings are provided below. The data will be further analysed and interpreted in subsequent peer reviewed papers.

• There are contrasts in population trends and land use within the two catchments: in the higher catchment in Ramche VDC, land is predominantly community forest with locals largely employed in subsistence farming on terraced slopes. Population was steady, with outward migration matching increased birth rates. Community members were concerned about a skills shortage to sustain the agricultural land. In recent years there has been a shift from cereal crops to vegetable farming. Locals in Ramche VDC are concerned about drying of the springs and increased prevalence of pests and diseases affecting the forest. Water scarcity is a concern during the pre-monsoon season and there is a government initiative to install further water supply sources in Ramche VDC using stream water. In the lower catchment in Madanpokhara VDC land is predominantly cultivated for commercial vegetable farming with crops sold in nearby towns. An influx of people to Madanpokhara as a result of the growing agricultural industry is placing increasing pressure on water supplies with growing populations and increased irrigation of land. Locals in Madanpokhara VDC are concerned about the insufficiency of spring water. However, the growing abstraction of groundwater through tube wells has underpinned the rapid expansion of irrigated agriculture, and arguably, the springs flows are becoming less important.
• There is a heavy reliance on springs for water supply in the Middle Hills, particularly at higher altitudes. Two principle types of springs have been identified i) diffuse springs which emanate from higher slopes and discharge to form the headwaters of incised mountain streams, and ii) discrete springs which appear to issues at topographical lows at lower elevations. The springs are typically perennial but with significantly reduced flows during the winter and pre-monsoon season. The springs have bicarbonate groundwater chemistry and general low overall mineralisation.
• Diffuse springs issuing from the higher slopes are reliant on recent monsoon rainfall and snow to sustain higher flows, but baseflows are sustained by groundwater storage within the weathered aquifer and will therefore have some inter-annual storage. Discrete springs issuing from the base of lower slopes are most likely to be fed from groundwater storage within the fractured aquifer network. Their relatively weak coupling to recent rainfall implies some inter-annual storage. Groundwater residence time indicators (CFC and SF₆) suggest a mean residence time of 10–20 years for baseflow, implying again some in built resilience. The general low storage of the groundwater environment suggests that none of the springs would be resilient to a long term reduction in precipitation.
• Stable isotope results for the diffuse springs in the higher slopes suggest that a reduction in precipitation or changes in the seasonality of rainfall would result in a more restricted groundwater capture zone for the springs and a lower year round flow. Stable isotope results for the lower discrete springs suggest a more localised but seasonally consistent groundwater capture zone. These springs may therefore be less vulnerable to changes in seasonal rainfall but may be susceptible to changes in the spatial rainfall patterns.
• Spring flows and water quality are vulnerable to changes in land use, for example deforestation, landslides and increased development. The presence of community forest land use in the higher slopes of the middle hills makes springs in these locations less vulnerable than springs nearer the settlements.
• There is anecdotal and field evidence of water scarcity during the pre-monsoon season, where spring flow is insufficient to meet the demands of the community. In some cases spring flow from larger springs is diverted to other supplies to meet demand while some households in Madanpokhara re-use domestic water on agricultural land. Formal water storage structures in the catchments are limited.
• In the lower catchment of Madanpokhara where floodplain and outwash deposits are present a proliferation of manually drilled shallow tubewells have been installed in the last 5–10 years. Groundwater abstracted from these tubewells is largely used for irrigation of agricultural land, use of the groundwater for domestic purposes is more-limited. The development of these groundwater resources has resulted in a thriving agricultural co- operative, secure livelihoods, inward migration and a growing population. It is unclear whether recharge to the floodplain aquifer balances groundwater abstracted from it. These shallow tubewells have increased the resilience of the local communities but are potentially vulnerable to over-exploitation as a result of population increase and economic growth as well as being sensitive to polluting activities.
• Groundwater sampled in tubewells along the margin of the floodplain is modern (~20 yrs MRT) with bicarbonate groundwater chemistry and no significant water quality concerns. Groundwater sampled from tubewells towards the centre of the floodplain appears to be older (~50 yrs MRT) with elevated concentrations of iron, manganese and arsenic detected at some sites.

Further work

To strengthen the evidence base in the Middle Hills, on-going flow and temperature monitoring of the springs sources is being undertaken by ISET-Nepal and a further 6 months of stable isotope samples have been collected and will be tested by the BGS laboratory. Once all data are available the following outputs will be developed: (1) data for the local Nepali communities; (2) a paper on groundwater within the Middle Hills; and (2) a second paper presenting the use of groundwater in Madanpokhara and the evolution of groundwater chemistry from the hillslopes through to the floodplain.

With a growing recognition of the importance of groundwater storage in the middle hills there is significant potential to further advance the characterisation of groundwater systems and investigate their resilience to change. Clearly, there is much work to be done. Systematic monitoring of groundwater, as springs flows, groundwater levels and chemistry would give a much better understanding of emerging trends. Likewise, monitoring current yields of springs and comparing to historic values at installation may allow some conclusions to be drawn about the trajectory of springflow. There are several initiatives underway within Nepal; the lessons learned from this current research, the methodologies used and the preliminary findings will be of value to these:

• ISET-Nepal has initiated a transboundary groundwater study in three Terai districts of Nepal in conjunction with Megh Pyne Abhiyan (MPA), Water Action and Advanced Center for Water Resources Development and Management (ACWADAM) of India. The scope of the study includes contextualizing transboundary water, with special reference to aquifers and participatory groundwater management in India and Nepal.
• ISET-Nepal, in collaboration with the Groundwater Resource Development Board, has undertaken some preliminary groundwater mapping of Nepal.
• IWMI has started a five-year research project on Nepal’s Middle Hills, funded by the Asia Development Bank (ADB). The project will investigate the hydrology of the Middle Hills, in particular the spring systems, and will focus on two river catchments in Western Nepal, near West Seti.
• ICIMOD are undertaking a short-term innovation project to assess springs in the water-deficient catchments of Jhikhu and Namo Buddha in Kavre district, east of Kathmandu. Rainfall data, spring flow data and information on water usage and water management practices will be collected as part of the project.
• The Groundwater Resources Development Board (GWRDB) has long-term aims to monitor springs in the middle hills. Inventories of the catchment springs are being collected and surveys of newly-drilled shallow tubewells in the Middle Hills are being undertaken. The GWRDB is also considering drilling observation boreholes on the metamorphic sediments of the middle-hills. In order to improve their groundwater testing capability the GWRDB have invested in laboratory equipment for groundwater stable isotope analysis.