The objective of work package 6 is to establish the spatio-temporal relationship between groundwater and surface water of the Karnali megafan and associated Bardia National Park. To be able to answer questions related to hydrological controls on natural functioning of the grasslands, we require data on aquifer system, groundwater and surface water levels, precipitation and vegetation dynamics. Hence, the work package also looks at establishing cooperation with other work packages such as 4, 5, 7, and 9.

Since October 2022, we have undertaken three fieldwork campaigns that focused on data collection. We have established cooperation with local partners such as National Trust for Nature Conservation (NTNC), International Maize and Wheat Improvement Center (CIMMYT), Nepalese laboratories and local workers to conduct our fieldwork campaigns.

Figure 1: ERT Survey in the Park

Figure 2: Groundwater monitoring well installed in the national park

Our current research seeks to generate insights on the hydrogeology of the Karnali megafan. Therefore, we used Electrical Resistivity Tomography to lithologically schematize the megafan. The geophysical fieldwork campaign was conducted during April-May 2023 in collaboration with Tribhuvan University. Data was collected from 21 sites. Using inverse modelling and adding information from adjacent borewell descriptions, we delineated subsurface lithological layers of Karnali megafan and its surroundings up to a depth of 100 m. The fan apex is found to have coarse sand and gravel layers in the subsurface while to the south fine to coarse sand layers are present. Near the Babai River to the east of the fan, a sand aquifer with silt and clay pockets exists.

Figure 3: Measuring groundwater inside the national park

The delineated aquifer will be used in the next phase of our study. For this we have installed 18 wells to monitor groundwater levels at locations both inside and around the park. Data is being collected during field visits along with technicians from NTNC. We have also conducted slug tests to get information about aquifer parameters like hydraulic conductivity. We will use this information to construct a numerical groundwater model to simulate groundwater levels, rain recharge, as well as surface water – groundwater interactions of the megafan and the park.

Output – We have presented two posters at the Netherlands Earth Sciences Conference 2024 (NAC 2024) and IAH World Groundwater Congress 2024 on lithological schematization of the Karnali megafan. Two master students have been engaged so far in this work package: Stephen Maycock (Master’s thesis): A protocol for sampling ecohydrological traits in Nepal’s Terai Arc Landscape and Clarisse Jahn (Tailor-made course) : Analysis of pumping tests and groundwater scenario of Banke district.