Water Demand: The water demand at the nodes (catchment and demand sites). The values are reported in cubic meters (m3).
Supply Delivered: The actual water that is supplied to meet the demand at the nodes. The values are reported in cubic meters (m3).
Unmet Demand: The deficit in the total supply in comparison to the demand at the nodes (m3).
The values are for the year 2050 in all the future scenarios. The values shown for the baseline period correspond to the base year 2000.
Scenario 1 – Baseline: Current water use is estimated under current water supply and water demand estimates from the census data for the year 2000. The reference scenario had three sectoral demands: domestic, agricultural and industrial. The year 2000 was taken as the baseline year as the 2000 demand data and hydrological outputs were easily available from the SWAT model.
Scenario 2 – Planned Water Resource Developments: Of the proposed WRDs, the Sapta Koshi High Dam, across the Koshi River near Chatara, is highly recommended by JICA (1985) as there is potential to build large storage of 8500 MCM. According to the report, the excess power produced annually in this project could be exported to India, and thus can promote healthy trans-boundary relationships, leading to economic growth. The Sapta Koshi High Dam project was initially identified in 1956 by the Government of India (GoI, 1981), with a 239 m high dam and a hydropower station located immediately downstream. The Sun Koshi Dam, proposed across the Sun Koshi River, was also initially identified in the GoI (1981) report. The site was selected near the confluence of Sun Koshi and Dudh Koshi with a proposed 147 m high dam. The Tamor project was proposed across the Tamor River near the confluence of Tamor and Sapta Koshi rivers. A 153m high dam was proposed with a hydropower station location directly downstream of the dam. The Dudh Koshi project was planned as a pondage type (low storage compared to the other storage dams) across the Dudh Koshi River, 28 km upstream of the confluence of the Sun Koshi and Dudh Koshi rivers.
Of the RORs, Upper Arun, Lower Arun and Arun III were placed along the Arun River, while the Sun Koshi HEP was placed along the Sun Koshi River. Also, the Tama Koshi River and the Bhote Koshi River each had one ROR. Further information on the construction and operation of the RORs can be obtained from JICA (1985, 2014) and NEA (2013) reports. The characteristics of the WRDs (e.g. gross storage, hydropower capacity, volume-elevation curve) were input into the WEAP model and run using the baseline hydrological setup. The domestic, agricultural and industrial demands were the same as in the baseline scenario.
Scenario 3 – Population Growth: Population increase rate, as assessed from the past three census reports (1991, 2001 and 2011) were used to estimate the population for 2050. For this scenario, only the population was changed in the WEAP while all the other model setup were similar to the baseline scenario.
Scenario 4 – Agricultural Growth: District wise agricultural statistics from three reports over the years 1991, 2001 and 2011 were used to assess 2050 cropped area. Trend analysis of the census statistics indicated a decreasing trend in some crops (e.g. cereals, vegetables and oilseeds), while other crops had an increasing trend (e.g. paddy, sugarcane, tobacco and jute). The WEAP model was then run with baseline conditions with the updated cropped type and area, under baseline conditions
Scenario 5 – Industrial Growth: District census reports were used to generate industrial growth trends across the basin. While the Chinese regions have no increase in industries, Nepal and India have a 30 and 40% increase in industrial units by 2050. Similar to the above scenarios, the baseline water supply and domestic and agricultural demands were the same with only the industrial demands altered.