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Global warming affected by human activities causes changes in the regime of rivers. Rivers are one of the most vital sources that supply fresh water. Therefore, management, planning, and proper use of rivers will be crucial for future climate change conditions. This study investigated the monitoring of hydrological drought in a future period to examine the impact of climate change on the discharging flow of the Zard River basin in Iran. Zard River is an important supplier of fresh and agricultural water in a vast area of Khuzestan province in Iran. A continuous rainfall-runoff model based on Soil Moisture Accounting (SMA) algorithm was applied to simulate the discharge flow under 10 scenarios (obtained from LARS-WG.6 software) of future climate change. Then, the Stream-flow Drought Index (SDI) and the Standard Precipitation Index (SPI) were calculated for each climate change scenario for the future period (2041–2060). The results of the meteorological drought assessment showed that near normal and moderate droughts had higher proportions among other drought conditions. Moreover, the hydrological drought assessment showed the occurrence of two new droughts (severe and extreme) conditions for the future period (2041–2060) that has never happened in the past (1997–2016). HIGHLIGHTS Examining two RCPs to evaluate runoff and precipitation in the future.; Using of Soil Moisture Accounting (SMA) to compute excessive rainfall and rainfall-runoff modeling.; Evaluating the interaction between SDI and SPI drought indices.; Five AOGCMs under two RCPs were tested in the drought monitoring.; Extreme droughts will occur in the future in this region and will decrease the water security.;

One of the potential impacts of climate change (CC) is the change on flood frequency and magnitude. Assessment of impact on floods involves many uncertainties. Difficulty in preparing reliable continuous time series of climate variables with fine time step and capturing extreme rainfalls for future climate scenarios has led to limited studies aimed at investigation of the change of flood regime due to CC. Weather Generators (WGs) have the potential for downscaling of GCMs (General Climate Models) outputs. However, WGs inabilities in relation to producing extreme rainfalls and low-frequency variabilities have caused WGs to receive limited attention in flood studies. In this study, a new WG model, that removes the aforementioned WGs' inabilities, is coupled with a continuous daily rainfall-runoff model to assess the CC impacts on floods of a basin in Iran. Changes in different characteristics of climate variables are applied in the downscaling procedure. Results indicated that, aside from the large uncertainty of emission scenarios, the climate change will lead to considerable increase in flood magnitude in the study basin. Copyright © 2011 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Summary: Efforts to understand and to quantify precipitation and its partitioning into runoff evapo-transpiration, and recharge are often hampered by the absence or paucity of appropriate monitoring systems. We applied methodologies for rainfall–runoff and groundwater recharge computations that heavily rely on observations extracted from a wide-range of global remote sensing data sets (TRMM, SSM/I, Landsat TM, AVHRR, AMSR-E, and ASTER) using the arid Sinai Peninsula (SP; area: 61,000 km2) and the Eastern Desert (ED; area: 220,000km2) of Egypt as our test sites. A two-fold exercise was conducted. Spatiotemporal remote sensing data (TRMM, AVHRR and AMSR-E) were extracted from global data sets over the test sites using RESDEM, the Remote Sensing Data Extraction Model, and were then used to identify and to verify precipitation events throughout the past 10 years (1998–2007). This was accomplished by using an automated cloud detection technique to identify clouds and to monitor their propagation prior to and throughout the identified precipitation events, and by examining changes in soil moisture (extracted from AMSR-E data) following the identification of clouds. For the investigated period, 246 of 327 events were verified in the SP, and 179 of 304 in the ED. A catchment-based, continuous, semi-distributed hydrologic model (Soil Water and Assessment Tool model; SWAT) was calibrated against observed runoff values from Wadi Girafi Watershed (area: 3350km2) and then used to provide a continuous simulation (1998–2007) of the overland flow, channel flow, transmission losses, evaporation on bare soils and evapo-transpiration, and groundwater recharge for the major (area: 2014–22,030km2) watersheds in the SP (Watir, El-Arish, Dahab, and Awag) and the ED (Qena, Hammamat, Asyuti, Tarfa, El-Quffa, El-Batur, Kharit, Hodein, and Allaqi) covering 48% and 51% of the total areas of the SP and the ED, respectively. For the investigated watersheds in the SP, the average annual precipitation, average annual runoff, and average annual recharge through transmission losses were found to be: 2955×106m3, 508×106m3 (17.1% total precipitation (TP)), and 463×106m3 (15.7% TP), respectively, whereas in the ED these values are: 807×106m3, 77.8×106m3 (9.6% TP), and 171×106m3 (21.2% TP), respectively. Results demonstrate the enhanced opportunities for groundwater development in the SP (compared to the ED) and highlight the potential for similar applications in arid areas elsewhere. The adopted remote sensing-based, regionalization approach is not a substitute for traditional methodologies that rely on extensive field datasets from rain gauge and stream flow networks, yet could provide first-order estimates for rainfall, runoff, and recharge over large sectors of the arid world lacking adequate coverage with spatial and temporal precipitation and field data. [Copyright &y& Elsevier]

Summary: Rising demands for fresh water supplies are leading to water management practices that are altering natural flow systems world-wide. One of the most devastated of these natural systems is the Tigris–Euphrates watershed that over the past three decades has witnessed the construction of over 60 engineering projects that eliminated seasonal flooding, reduced natural flow and dramatically reduced the areal extent (1966: 8000km2; 2002: 750km2) of the Mesopotamian Marshes downstream. We constructed a catchment-based continuous (1964–1998) rainfall runoff model for the watershed (area: 106 km2) using the Soil Water Assessment Tool (SWAT) model to understand the dynamics of the natural flow system, and to investigate the impacts of reduced overall flow and the related land cover and landuse change downstream in the marshes. The model was calibrated (1964–1970) and validated (1971–1998) against stream flow gauge data. Using the calibrated model we calculated the temporal variations in the average monthly flow rate (AMFR), the average monthly peak flow rate (AMPFR), and annual flow volume (AFV) of the Tigris and Euphrates into the marshes at a location near Al-Basrah city (31°N, 47.5°E) throughout the modeled period. Model results indicate that the AMPFR (6301m3/s) and average annual flow volume (AAFV: 80×109 m3/yr) for period A (10/1/1965–09/30/1973), preceding the construction of the major dams is progressively diminished in periods B1 (10/1/1973–09/30/1989; AMPFR: 3073m3/s; AAFV: 55×109 m3/yr) and B2 (10/1/1989–09/30/1998; AMPFR, 2319m3/s; AAFV: 50×109 m3/yr) that witnessed the construction of the major dams (B1: Keban, Tabqa, Hamrin, Haditha, Mosul, Karakaya; B2: Ataturk) due to the combined effects of filling artificial lakes, evaporation and infiltration of impounded water and its utilization for irrigation purposes. To investigate the impacts of reduced flow on the areal extent of the marshes, we examined the variation in marsh size extracted from temporal satellite data (1966, 1975, 1976, 1977, 1984, 1985, 1986, 1987) acquired around the same approximate time period (July to September) of the year versus simulated AFV for the period preceding the onset (1987) of major local engineering projects (e.g., Crown of Battles River, Loyalty to the Leader Canal, Mother of Battles River) in and around the investigated marshes. Results indicate that the areal extent of the Central and Al-Hammar marshes (e.g., 1966: 7970km2, 1977: 6680km2, 1984: 5270km2) decreases with a decrease in AFV (e.g., 1966: 60.8×109 m3, 1977: 56.9×109 m3, 1984: 37.6×109 m3). Using a relationship that describes the impact of reduced AFV on the areal extent of the marshes, we evaluated the impact of additional reductions in flow that will result from the implementation of the planned engineering projects on the Tigris–Euphrates system over the next few years. Upon completion of the ongoing South Eastern Anatolia project, with projected reductions in AFV exceeding 5×109 m3/yr, the sustainable marshes in the Central and Al-Hammar area will be reduced by at least an additional 550km2. [Copyright &y& Elsevier]