# Assessment of Drought Severity and Vulnerability in the Lam Phaniang River Basin, Thailand
## 3 Results and Discussion
### Analysis of River Basin Water Balance  
To capture relevant hydrological processes and river basin water balance, the WEAP model was applied on a monthly basis to incorporate the quantity of water available and the connections among all prioritized users (abstractions, discharge, water transfer, etc.) within the Lam Phaniang River Basin. Based on the WEAP simulation results, the values of all computed variables, i.e., runoff, water demand, and water shortage, were transformed \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Land Use Type**} & \multicolumn{8}{c}{**Period**} \\ \cline{2-10}  & **2015** & **2021–2040** & **2041–2060** & **2061–2080** & **2081–2100** & **2081–2100** \\ \cline{2-10}  & **Area** & **Area** & **Change** & **Area** & **Change** & **Area** & **Change** & **Area** & **Change** \\ \hline Aquaculture land & 1.3 & 1.3 & 0.0 & 1.3 & 0.0 & 1.3 & 0.0 & 1.3 & 0.0 \\ Field crop & 435.1 & 216.7 & \(-\)218.4 & 161.6 & \(-\)273.5 & 143.3 & \(-\)291.8 & 138.8 & \(-\)296.3 \\ Forest land & 407.1 & 366.6 & \(-\)40.5 & 337.5 & \(-\)69.6 & 312.5 & \(-\)94.6 & 291.6 & \(-\)115.5 \\ Horticulture & 0.9 & 0.9 & 0.0 & 0.9 & 0.0 & 0.9 & 0.0 & 0.9 & 0.0 \\ Miscellaneous land & 47.0 & 47.0 & 0.0 & 47.0 & 0.0 & 47.0 & 0.0 & 47.0 & 0.0 \\ Orchard & 21.4 & 11.1 & \(-\)10.3 & 9.7 & \(-\)11.7 & 9.5 & \(-\)11.9 & 9.7 & \(-\)11.7 \\ Paddy field & 642.5 & 665.3 & 22.8 & 673.1 & 30.6 & 677.3 & 34.8 & 679.8 & 373.3 \\ Pasture and farmhouse & 0.7 & 0.7 & 0.0 & 0.7 & 0.0 & 0.7 & 0.0 & 0.7 & 0.0 \\ Perennial crop & 183.7 & 407.6 & 223.9 & 473.3 & 289.6 & 503.5 & 319.8 & 519.2 & 335.5 \\ Urban and built-up land & 97.2 & 119.6 & 22.4 & 131.7 & 34.5 & 140.9 & 43.7 & 147.8 & 50.6 \\ Water body & 48.0 & 48.0 & 0.0 & 48.0 & 0.0 & 48.0 & 0.0 & 48.0 & 0.0 \\
**Total** & **1884.80** & **1884.80** & **1884.80** & **1884.80** & & **1884.80** & & **1884.80** & \\ \hline \hline \end{tabular} Note.: The unit of area and change is km\({}^{2}\).  
\end{table} 
Table 3: Changes in future land use patterns compared to the year 2015. Figure 6: Observed and simulated monthly discharge during (**a**) calibration period and (**b**) validation period, at gauging station E.68A. into the mean monthly water balance over the specified time horizons (2000-2100), which was tabulated in Table 4. Interestingly, from the end of the rainy season until the middle of the dry season (October to February), runoff was found to be decreased due to the decrease in rainfall. In contrary, water demand showed the opposite trend to the runoff due to the growing of second rice crops, maize, cassava, and sugarcane after the rainy season, as indicated in the cropping calendar of the Nong Bua Lamphu Provincial Agricultural Extension Office. As a result, water shortage was noticeable during the aforementioned period. In detail, the increase in future annual runoff under RCP 8.5 was higher than RCP 4.5 for all projected periods, while an increase was also found for both RCPs 4.5 and 8.5 scenarios compared to the baseline, except under RCP 4.5 for 2061-2100 due to low rainfall at some certain periods of these years (see Figure 5c and Table 4). The future annual water demand was found to decrease from the baseline due to a large increase in future runoff, especially during 2061-2080 under RCP 8.5, with the largest reduction of approximately 31.81%. Of course, the significant increase in future annual runoff and decrease in future annual water demand would probably ensure sufficient water availability for satisfying long-term average requirements, and also for hedging against water shortages, with a maximum decrease of 51.61% during 2061-2080 under RCP 8.5 compared to the years 2000-2017 (288.93 million m\({}^{3}\)). However, due to a certain range of total annual water deficit between supply and demand from 139.82 to 288.93 million m\({}^{3}\)/year, it is still expected that the Lam Phaniang River Basin would probably continue to suffer from a scarcity of water. This interpretation is in line with the findings of [PERSON] et al.