Watershed runoff is essential for water management. However, runoff materials are lacking in poorly gauged catchments and not always accessible. Microwave remote sensing offers emerging capabilities for hydrological simulation. In this study based on multi-satellite retrievals for Global Precipitation Measurement (IMERG), Tropical Rainfall Measuring Mission (TRMM) products, and World Meteorological Organization (WMO) interpolated precipitation data, we simulated runoff using a variable infiltration capacity (VIC) model and studied the differences among the results. Then, we analyzed the impacts of the runoff on a moderate-resolution imaging spectroradiometer vegetation leaf area index (LAI) during dry seasons. The results showed that (1) IMERG V5 and TRMM products are capable of monitoring the night-day rainfall diurnal cycle and have higher correlations than the WMO daily observation interpolations. However, the WMO shows less overestimation of total precipitation than remote-sensing precipitation; (2) in the downstream, the TRMM shows better runoff simulation accuracy in the tributaries, and the WMO shows better results in the mainstreams. Therefore, at basin outlets in mainstreams, the Nash-Sutcliffe efficiency coefficients of monthly runoff by the WMO are higher than the simulations by the TRMM; (3) for the whole basin during dry seasons, the LAI variation is correlated with the outlet runoff, which is similar to the correlation with threeto six-month accumulated precipitation. TRMM products can be used to depict both precipitation deficit and runoff deficit, which cause vegetation variations. Our research suggests the potential of microwave precipitation products for detailed watershed runoff simulations and water management.Water 2019, 11, 818 2 of 15 vegetation conditions, such as the normalized difference vegetation index (NDVI), a measure of the greenness or vigor of vegetation. The higher its value, the larger the vegetation density is; a low NDVI indicates stressed or small-leaf vegetation [3]. However, the NDVI can often be saturated across densely vegetated regions or during high-growth periods [4], whereas the leaf area index (LAI) has been shown to be more effective for drought monitoring [5,6]. Previous studies have shown that the multi-temporal accumulation precipitation index has a strong correlation with vegetation response [7][8][9]. The evolution of meteorological hydrological factors affects vegetation growth [10]. Both factors-precipitation and runoff-that cause variations in the vegetation LAI, should be examined separately.Dynamic watershed runoff is essential to the water supply, irrigation management, and accurate flood prediction and control. River discharge at a site is an integrated signal of water cycle processes over the catchment. However, many catchments lack runoff observation. A hydrological model is an important tool to understand water cycle processing and to fill the gaps of runoff information. The simulation accuracy mainly depends on model mechanisms and data input. The th...

This study aimed at quantifying the impacts of climate and land use changes on flood damage on different flood occurrences. A Hydrologic Engineering Center’s Hydrologic Modeling System (HEC-HMS) model was calibrated for the period 2005–2011 and validated in the period 2012–2017, and was used to generate hydrographs using rainfall during the period 2020–2039 from CNRM-CM5, IPSL-CM5A-MR, and MPI-ESM-LR climate models under Representative Concentration Pathways (RCPs) 4.5 and 8.5. A Hydrologic Engineering Center’s River Analysis System (HEC-RAS) model for use in generating inundation maps from hydrographs produced by HEC-HMS was calibrated and validated for 2010 and 2011 period, respectively. The climate and land use changes showed insignificant impacts on the extent of floods during 25-, 50-, and 100-year flood events, i.e., inundation in 2039 under RCP 4.5 is smaller than baseline (2000–2017) by 4.97–8.59 km2, whereas a larger difference of inundation is found for RCP 8.5 (0.39–5.30 km2). In contrast, the flood damage under RCP 4.5 (14.84–18.02 million US$) is higher than the baseline by 4.32–5.33 million US$, while the highest was found for RCP 8.5 (16.24–18.67 million US$). The agriculture was the most vulnerable, with a damage of 4.50–5.44 million US$ in RCP 4.5 and 4.94–5.72 million US$ in RCP 8.5, whereas baseline damages were 4.49–6.09 million US$. Finally, the findings are useful in the delivery of flood mitigation strategies to minimize flood risks in the lower Nam Phong River Basin.

The Yang River Basin, Thailand, has always been subjected to flooding, but due to recent developments in land use there is an increase in the vulnerability in several parts of the river basin. To mitigate impacts of flooding, both structural and non-structural measures can be taken. This paper discusses three scenario simulations focusing on flood retardation, retention, and damage mitigation measures. A main tributary was simulated by a process-based hydrological model (SWAT) and coupled to the 1D/2D SOBEK river routing model. The first scenario focused on retarding basins, the so-called natural flood storage, to reduce downstream flood flows by storing excess floodwater in low-lying areas and releasing it after the peak has passed. The second scenario concerned a green river (bypass channel) to provide storage and drainage through a large, shallow retardation basin, and an outlet for water discharge from upstream. The third scenario concerned the effect of dikes to protect areas from inundation. The results show that the green river is the most appropriate solution since it can potentially reduce a 1% to a 10% per year flood event, with a reduction of peak discharges of 14% in comparison to 9.2% reduced by natural flood storage. RÉ SUMÉLe bassin du fleuve Yang, la Thaïlande, a toujours été soumis aux inondations, mais en raison de l'évolution récente de l'utilisation des terres il ya une augmentation de la vulnérabilité dans plusieurs parties du bassin de la rivière. Pour atténuer les impacts des inondations, à la fois structurelles et des mesures non structurelles peuvent être prises. Ce document traite de trois simulations de scénarios mettant l'accent sur le retard des inondations, la conservation, et des mesures d'atténuation des dommages. Un affluent principal a été simulée par un modèle basé sur les processus hydrologiques (SWAT) et couplé à la rivière SOBEK 1D/2D routage modèle. Le scénario s'est d'abord concentré sur les bassins de retardement, ce qu'on appelle le stockage de ces eaux naturelles, pour réduire les flux d'inondation en aval en stockant les eaux de crue excès dans les zones basses et de la libérer après le pic est passé. Le deuxième scénario concerne une rivière verte (canal de dérivation) d'assurer le stockage et le drainage au moyen d'un grand bassin peu profond retard, et une sortie de rejet d'eaux d'amont. Le troisième scénario concerne l'effet des digues pour protéger les zones de l'inondation. Les résultats montrent que la rivière verte est la solution la plus appropriée, car elle peut potentiellement réduire de 1% à 10% par année de l'événement inondation, avec une réduction des débits de pointe de 14% en comparaison à 9,2% réduit par un stockage d'inondation naturelles.

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When the severity of exposure to flood is being addressed, several related concerns have always been raised to draw attention on a growing flood threat. In relation to this, the extraordinary insight into the seriousness of land use and rainfall changes that could greatly exacerbate flood impacts would need to be highlighted. The importance of the aforementioned issue lies in the main objective of quantifying consequences of how changes in land use and rainfall affect the hydrological processes in the lower Nam Phong River Basin. The use of Hydrologic Modeling System (HEC-HMS) simulation model would add robustness and predictability to the overall results. It was apparent from the calibration and validation processes that there are reasonably close agreement between observed and simulated discharges at Ban Nong Hin gauging station (E.22A), with good correlation coefficients (ENS= 0.78, r2= 0.81 and ENS= 0.77, r2= 0.82, respectively). Thereafter, different what-if scenarios were conducted to determine impacts of land use changes in 2001, 2011 and 2057 and extreme rainfall with different return periods of 10-, 50-and 100-years on hydrological responses. A slight increase in peak flows were equal to 4% and 1%, as a consequence of the change from 2001 land use conditions to 2011 and 2057, respectively. Conversely, a large increase in peak discharges was expected to be 13%, 20% and 27% when the 2001 rainfall event was adjusted to the projected changes in rainfall corresponding to 10-, 50-and 100-year return periods, respectively. In brief, insignificant relation between hydrological response and land use changes was obviously found, but it was of particular significance due to changes in rainfall extremes. Taken together, obtained findings can then be used as a baseline for water resources planning, development and management, as well as flood management perspective.

Sustainable water resources management and community engagement are essential for water security. Referring to the above context, this study proposed to carry out an assessment of community engagement for irrigation water management in the Nam Haad Left Irrigation Project (NHLIP). The household and community level practices and the farmers' levels of participation in irrigation water management of the NHLIP were carefully considered. From respondents' responses, the results revealed that a husband-wife partnership plays a remarkable role in irrigation water management of the NHLIP for rice farming. The results also proved that most of the respondents engage with a high participation level in managing irrigation water of the NHLIP project as illustrated by a high score of 3.80 on the five-point Likert scale. To determine the significance of each activity on farmers' levels of participation in irrigation water management of the NHLIP, a stepwise multiple regression analysis was employed and the standardized regression equation for determining overall participation levels can be presented as: Y = 0.538x 1 + 0.831x 8 + 0.534x 14 + 0.607x 18 + 7.572. Finally, the outcomes of this study indicated the willingness of participation in cooperating and supporting the activities related to the improvement and management of the NHLIP project.

The aim of this research was to identify optimal choices in decision support systems for network reservoirs by using optimal rule curves under four scenarios related to water scarcity and overflow situations. These scenarios were normal water shortage, high water shortage, normal overflow and high overflow situations. The application of various optimization techniques, including Harris Hawks Optimization (HHO), Genetic Algorithm (GA), Wind-Driven Optimization (WDO) and the Marine Predator Algorithm (MPA), in conjunction with a reservoir simulation model, was conducted to produce alternative choices, leading to suitable decision-making options. The Bhumibol and Sirikit reservoirs, situated in Thailand, were selected as the case study for the network reservoir system. The objective functions for the search procedure were the minimal average water shortage per year, the minimal maximum water shortage and the minimal average water spill per year in relation to the main purpose of the reservoir system using the release criteria of the standard operating policy (SOP) and the hedging rule (HR). The best options of each scenario were chosen from 152 options of feasible solutions. The obtained results from the assessment of the effectiveness of alternative choices showed that the best option for normal water scarcity was the rule curve with the objective function of minimal average water shortage per year, using HR and recommended SOP for operation, whereas the best option for high-water shortage situation was the rule curves with objective function of minimal of maximum water shortage using HR and recommended HR for operation. For overflow situation, the best option for normal overflow situation was the rule curves with objective function of minimal average water spill per year using HR and the recommended SOP for operation, whereas the best option for the high overflow situation was the rule curve with the objective function of minimal average water spill per year using HR and the recommended HR for operation. When using the best curves according to the situation, this would result in a minimum water shortage of 153.789 MCM/year, the lowest maximum water shortage of 1338.00 MCM/year, minimum overflow of 978.404 MCM/year and the lowest maximum overflow of 7214.00 MCM/year. Finally, the obtained findings from this study would offer reliability and resiliency information for decision making in reservoir operation for the multi-reservoir system in the upper region of Thailand.

The Lam Phaniang River Basin is one of the areas in Northeast Thailand that experiences persistent drought almost every year. Therefore, this study was focused on the assessment of drought severity and vulnerability in the Lam Phaniang River Basin. The evaluation of drought severity was based on the Drought Hazard Index (DHI), which was derived from the Standardized Precipitation-Evapotranspiration Index (SPEI) calculated for 3-month (short-term), 12-month (intermediate-term), and 24-month (long-term) periods. Drought vulnerability was assessed by the Drought Vulnerability Index (DVI), which relied on water shortage, water demand, and runoff calculated from the WEAP model, and the Gross Provincial Product (GPP) data. A drought risk map was generated by multiplying the DHI and DVI indices, and the drought risk level was then defined afterwards. The CNRM-CM5, EC-EARTH, and NorESM1-M global climate simulations, and the TerrSet software were used to evaluate the potential impacts of future climate under RCPs 4.5 and 8.5, and land use during 2021–2100, respectively. The main findings compared to baseline (2000–2017) revealed that the average results of future rainfall, and maximum and minimum temperatures were expected to increase by 1.41 mm, and 0.015 °C/year and 0.019 °C/year, respectively, under RCP 4.5 and by 2.72 mm, and 0.034 °C/year and 0.044 °C/year, respectively, under RCP 8.5. During 2061–2080 under RCP 8.5, the future annual water demand and water shortage were projected to decrease by a maximum of 31.81% and 51.61%, respectively. Obviously, in the Lam Phaniang River Basin, the upper and lower parts were mainly dominated by low and moderate drought risk levels at all time scales under RCPs 4.5 and 8.5. Focusing on the central part, from 2021–2040, a very high risk of intermediate- and long-term droughts under RCPs 4.5 and 8.5 dominated, and occurred under RCP 8.5 from 2041–2060. From 2061 to 2080, at all time scales, the highest risk was identified under RCP 4.5, while low and moderate levels were found under RCP 8.5. From 2081–2100, the central region was found to be at low and moderate risk at all time scales under RCPs 4.5 and 8.5. Eventually, the obtained findings will enable stakeholders to formulate better proactive drought monitoring, so that preparedness, adaptation, and resilience to droughts can be strengthened.