Title
Understanding headwater baseflow contributions to the overall water supply of the Kathmandu Valley, Nepal
Author
Brouwer, Wietske (TU Delft Civil Engineering & Geosciences)
van Hamel, Amber (TU Delft Civil Engineering & Geosciences)
van Haren, Mick (TU Delft Civil Engineering & Geosciences)
Kindermann, Paulina (TU Delft Civil Engineering & Geosciences)
Verboeket, Rik (TU Delft Civil Engineering & Geosciences)
Contributor
Bogaard, T.A. (mentor)
Davids, J.C. (mentor)
Degree granting institution
Delft University of Technology
Date
2020-09
Abstract
The Kathmandu Valley in Nepal is facing the combined effects of population growth, rapid urbanization, economic development, and climate change. This results in serious water management challenges: growing freshwater demands, declining water tables, drying of streams, and deteriorating water quality. Insufficient surface water supplies have led to increased reliance on groundwater, especially during the dry winter and pre-monsoon seasons (November - May). Despite groundwater’s importance, it is sparsely measured, poorly understood, and insufficiently managed. As it is difficult and costly to measure all groundwater extractions in the Valley, a water balance approach is an alternative method to estimate total net groundwater pumping. Therefore, the aim of this research was to develop and evaluate potential methods for quantifying total pre-monsoon baseflow supplies by extrapolating baseflow measurements of a subsample of watersheds to unmeasured watersheds. Estimated baseflow was used, together with other water balance fluxes and changes in storage, to evaluate net groundwater pumping in the Valley. Three different methods were used: (1) Spatial Analysis, (2) Regression Model, and (3) Black Box (machine learning). All methods relied on streamflow data from 2017 to 2019, collected by citizen scientists from S4W-Nepal. Based on the three methods we presented, we cautiously conclude that it is possible to determine the pre-monsoon baseflow contributions from a sub-sample of head water catchments. Total baseflow estimates for the Valley using Spatial Analysis, Regression Model, Black Box were 2.32, 2.30, 2.65 m3/s respectively. These values show orders of magnitude that correspond with expected values. By using the average baseflow values of all three methods, we were able to close the water balance and make an assumption for the net groundwater pumping in the Valley. Based on a population of 3.5 million, a net groundwater extraction of 96 L/person/day during pre-monsoon was found. This striking outcome emphasizes the need for more discharge and groundwater extraction measurements, to decrease the uncertainties and to refine the methods.
Subject
Baseflow calculation
Hydrology
Kathmandu Valley
Nepal
Machine Learning
Regression Model
Spatial Analysis
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Part of collection
Student theses
Document type
student report
Rights
© 2020 Wietske Brouwer, Amber van Hamel, Mick van Haren, Paulina Kindermann, Rik Verboeket