An Assessment of the Monsoon Water Situation in the Kathmandu Valley: Data collection and analysis of flow, water quality, land use and demand

Kathmandu, the capital of Nepal, is under increasing water stress. A rising water demand in the Kathmandu Valley is initiated by urbanisation with a rate of 4.7 % per year and amplified by a growing trend of per capita water consumption. At the same time, water availability seems to deteriorate. However, the severity of the problem is hardly known due to immense data gaps. This research aims to (1) estimate the urban water demand from literature research, (2) collect new field data about spring and stream flow, water quality, and ecological stream health, and (3) analyse remotely sensed data in order to characterise the linkages and inter-dependencies between land use, hydrology, and water quality in the Kathmandu Valley. The field data were collected in August and September 2016 and helped to get a decent picture of the water situation. The landuse classification performed using Landsat 8 images had an accuracy of 88 % and proved to be a meaningful source of data to link to the other research topics. Automated SEBAL was attempted to be used for computing evapotranspiration estimates but cannot successfully be used in mountainous areas yet. Penman-Monteith equation was used as alternative. A simplified water balance was performed for the months of August and September 2015. The outcome showed estimates to be 2, 2 x 106 m3/d for ET, 5.6 x 106 m3/d for precipitation, 2.0 x 106 m3/d for the Bagmati outflow and 1.4 x 106 m3/d for groundwater infiltration. To be able to comment on long term groundwater depletion, an annual water budget needs to be performed. The clearest influence on water quality parameters (pH, DO, EC and Rapid Stream Assessment class) was found to be the presence of developed area. With more than 20 % developed area within the considered sub-watershed, the water becomes of such poor quality that it cannot be used for any purpose without extensive treatment. In the headwater areas of the Valley, a significant amount of water with a higher quality (i.e. drinking water) is found in the streams. In September 2016 the total inflow of drinkable water to the Valley floor was estimated to be at least 1.0 x 106 m3/d. This value cannot be considered as fully available for anthropogenic purposes, as water needs to remain in the streams in order to not jeopardise ecosystem services and other functions.Civil Engineering and Geoscience

Quantifying the connections: linkages between land-use and water in the Kathmandu Valley, Nepal

Land development without thoughtful water supply planning can lead to unsustainability. In practice, management of our lands and waters is often unintegrated. We present new land-use, ecological stream health, water quality, and streamflow data from nine perennial watersheds in the Kathmandu Valley, Nepal, in the 2016 monsoon (i.e., August and September) and 2017 pre-monsoon (i.e., April and May) periods. Our goal was to improve understanding of the longitudinal linkages between land-use and water. At a total of 38 locations, the Rapid Stream Assessment (RSA) protocol was used to characterize stream ecology, basic water quality parameters were collected with a handheld WTW multi-parameter meter, and stream flow was measured with a SonTek FlowTracker Acoustic Doppler Velocimeter. A pixel-based supervised classification method was used to create a 30-m gridded land use coverage from a Landsat 8 image scene captured in the fall of 2015. Our results indicated that land-use had a statistically significant impact on water quality, with built land-uses (high and low) having the greatest influence. Upstream locations of six of the nine watersheds investigated had near natural status (i.e., river quality class (RQC) 1) and water could be used for all purposes (after standard treatments as required). However, downstream RSA measurements for all nine watersheds had RQC 5 (i.e., most highly impaired). Generally, water quality deteriorated from monsoon 2016 to pre-monsoon 2017. Our findings reinforce the importance of integrated land and water management and highlight the urgency of addressing waste management issues in the Kathmandu Valley.Water ResourcesTransport and Logistic