Due to the above mentioned peculiarities of Zambezidischarge in downstream sections, we focussed on the simulation results averaged over the land-surface – thereby excluding the confound- ing impacts of reservoirs – to learn more about the hydrology in the context of the seasonal water balance (see Fig. 9 ). The hydrology in the Zambezi basin is characterized by representing a water limited system – as opposed to energy limited. Already under historic climate the potential evapo- transpiration cannot be met by the actual evapotranspiration (see Fig. 9 ), simply because there is not enough water stored in the soil due to insufﬁcient annual precipitation amounts. Therefore, any increases in temperature – and consequently increases in potential evapotranspiration – have a small impact on discharge. In contrast, small changes in precipitation have large impacts on discharge. This was already observed in the past, where discharge is considerably larger in wet years than in dry years and the model simulations are well in line with this observation (see Fig. 8 ). Under such condi- tions any projections with climate models have to be interpreted with caution – only small variations (increases/decreases) in precipitation projections cause large differences in the impact on discharge. This was also conﬁrmed by the sensitivity tests (see Table 5 and Fig. 10 , bottom) – where a decrease of precipitation by −10% caused a decrease in discharge by almost −850 m 3 /s, or −32%. Note that this high sensitivity of discharge to precipitation contrasts the conclusions of Beck and Bernauer (2011) that climate has relatively small effects on water availability in the Zambezi basin, which may be related to their approach of calibration to long-term average conditions.
Southern Africa, and the ZambeziRiver Basin (ZRB) in particular, are bound to face significant challenges related to their waterresources in the coming decades. On the one hand growing population and booming economic activity will undoubtedly increase the pressure exerted on natural ecosystems, be it in terms of land use changes, direct water abstractions for irrigation, or increased evaporation from new hydropower schemes. On the other hand, studies indicate that climate change is likely to have a strong impact on the basin’s climate and runoff characteristics (Intergovernmental Panel on Climate Change (IPCC), 2001). Presented what can be classified as worrying figures, Arnell (1999) found that the ZRB can witness decreased precipitation (~15%), increased potential evaporative losses (~15-25%), and diminished runoff (~30-40%).
The Krishna river basin, India was selected as study area due to its semi-arid nature, and vulnerability to climate change, owing to the erratic distribution of rainfall along with warmer climatic conditions. Few studies have been conducted to analyse the climate change impact on waterresources of the Krishna river basin. However, these studies use the greenhouse gas (GHG) and Special Report on Emissions Scenarios (SRES) scenarios, which carry an enormous uncertainty in the assumption of factors such as economic development, population growth, and developed technology ( Soro et al., 2017 ). For instance, using the GHG scenario, Gosain et al. (2006) concluded the Krishna basin to experience regular or seasonal water-stressed conditions in future, due to a decrease of precipitation and water yield. Kulkarni et al. (2014) projected an increasing trend in annual precipitation, surface runoff, water yield and actual evapotranspiration in future (2041-70), displaying no significant changes in these parameters in the early century (2011- 40) using the SRES scenario. In both these studies, a single GCM data was used without any bias correction, while performing calibration at the only one-gauge station. Mishra and Lilhare (2016) projected an increasing trend of water balance components along with rainfall and air temperature in Krishna river basin under future climate scenarions (CMIP5 models with RCP 4.5 and 8.5 scenarios).
Some of the possible water resource developments within the basin have the potential to be in conflict with each other and many of these conflicts could be exacerbated by future changes in the amount or patterns of variation of the avail- able water resource that may result from climate change. In- deed, the basin has been identified by the World Water As- sessment as having the potential for water-related disputes (Wolf et al., 2003). It is therefore important to establish an approach that can be used to assess the possible changes as a basis for resolving the potential conflicts and developing appropriate management strategies. This paper represents an assessment of climate change scenarios on the water budget and waterresources availability in the Okavango River basin. In this study, the Okavango River was one of a number of river systems for which a unified climate change impact assessment was conducted, coordinated under the QUEST- Global Scale Impacts project, funded by the UK Natural Environment Research Council (NERC). The work repre- sents an extension of the work that was completed during two previous EU projects designed to establish and evaluate water resource estimation tools that are appropriate for this data scarce region. The first project (WERRD – Water and Ecosystem Resources in Regional Development) applied the Pitman monthly rainfall-runoff model to simulate the natu- ral hydrology of the basin (Andersson et al., 2003; Hughes
Performance of SDSM downscaling based on NCEP and GCMs predictors at Langtang, Kyanging are evaluated using statistical properties of daily climate data. It was found that the application of SDSM for statistical downscaling is suitable for developing daily climatescenarios. To demonstrate the procedure of developing scenarios, SDSM is applied, based on daily outputs of common climate variables from GCMs simulation, which has been widely used in the development of daily climatescenarios, and the results can be used in many areas of climate change impact studies. According to this study, the autumn temperature is much warmer compared to winter, spring and summer. The precipitation is increased for NCEP calibrated scenarios for spring, summer and autumn, whereas in winter it is decreased. The model generally projected an increase of precipitation during summer and spring, and a decrease during winter and autumn seasons. However, maximum projected discharge will increase for all seasons except for spring compared to a minimum projected discharge in summer.
This study is a part of the Himalayan Climate Change Adaptation Programme (HICAP), which is funded by the Ministry of Foreign Affairs, Norway and Swedish International Development Agency (Sida). This work is partly financed through the research program VENI of the Netherlands Organization for Scientific Research (NWO). We acknowledge the World Climate Research Program’s Working Group on Coupled Modeling, which is responsible for CMIP5, and we thank the climatemodelling groups for producing and making available their model output. We thank the Nepal Department of Hydrology and Meteorology, the International Water Management Institute Pakistan, the Pakistan Water and Power Development Authority and the Pakistan Meteorological Department for making available discharge data. Furthermore, we thank J. Sheffield for correcting errors in the Princeton Global Meteorological Forcing data set over the studied region and S. Bajracharya for overall support in the project.
We acknowledge that the considered climate change and reservoir operations also impact on several other factors (e.g. Dugan et al., 2010; Kummu et al., 2010; Ziv et al., 2012), but in order to maintain focus we only examine the hydrolog- ical impacts. Moreover, although the analysed drivers (i.e. reservoir operation and climate change) are often seen as the most important factors for future hydrological changes in the Mekong (e.g. Keskinen et al., 2010; Mekong River Commis- sion, 2010c), they are not the only driving forces causing changes in the hydrology and water-related resources. Others include, for example, irrigation expansion, inter-basin water transfers, land use changes, and urbanisation (see also Pech and Sunada, 2008). For example the impact of expanded irri- gation, if realised as planned, might have significant impacts on the flow (Hoanh et al., 2010; Mekong River Commission, 2010c). The impact of irrigation is expected to be opposite to the impacts of reservoir operation on stream flows dur- ing the dry season, which means that the irrigation may re- duce the water level increase of dry season months caused by reservoir operations. Consequently, the cumulative impacts of different development plans and climate change – includ- ing estimates derived from several GCMs – should therefore be subject to further studies, building on and extending al- ready existing studies (see e.g. Hoanh et al., 2010; Mekong River Commission, 2010c).
Received: 26 March 2019; Accepted: 18 April 2019; Published: 24 April 2019 Abstract: This article illustrates the impact of potential future climatescenarios on water quantity in time and space for an East African floodplain catchment surrounded by mountainous areas. In East Africa, agricultural intensification is shifting from upland cultivation into the wetlands due to year-round water availability and fertile soils. These advantageous agricultural conditions might be hampered through climate change impacts. Additionally, water-related risks, like droughts and flooding events, are likely to increase. Hence, this study investigates future climate patterns and their impact on waterresources in one production cluster in Tanzania. To account for these changes, a regional climate model ensemble of the Coordinated Regional Downscaling Experiment (CORDEX) Africa project was analyzed to investigate changes in climatic patterns until 2060, according to the RCP4.5 (representative concentration pathways) and RCP8.5 scenarios. The semi-distributed Soil and Water Assessment Tool (SWAT) was utilized to analyze the impacts on waterresources according to all scenarios. Modeling results indicate increasing temperatures, especially in the hot dry season, intensifying the distinctive features of the dry and rainy season. This consequently aggravates hydrological extremes, such as more-pronounced flooding and decreasing low flows. Overall, annual averages of water yield and surface runoff increase up to 61.6% and 67.8%, respectively, within the bias-corrected scenario simulations, compared to the historical simulations. However, changes in precipitation among the analyzed scenarios vary between −8.3% and +22.5% of the annual averages. Hydrological modeling results also show heterogeneous spatial patterns inside the catchment. These spatio-temporal patterns indicate the possibility of an aggravation for severe floods in wet seasons, as well as an increasing drought risk in dry seasons across the scenario simulations. Apart from that, the discharge peak, which is crucial for the flood recession agriculture in the floodplain, is likely to shift from April to May from the 2020s onwards.
In Nantes (France) important overflowings from the combined sewer network towards the Erdre, a tributary of the Loire, occur regularly and contribute to the pollution of the water resource. The present paper intends to assess the impact of climate change and of the different urban developmentscenarios on overflowing volumes of the sanitary sewer network in the natural environment. It proposes and discusses a method using climate model outputs at the temporal and spatial resolutions available for users (daily step and a regional resolution) without an additional downscaling stage. The future evolution of overflowing is simulated by a hydrological model of the combined sewer system of Nantes at a daily time step. This model uses daily recorded data for six years. The preliminary results of this case study indicate that, in Nantes, climate change might result in a decrease of total overflows from the combined sewer network towards the Erdre. On the other hand, the increasing population associated to the urban development might accentuate overflowings. This study moderates different developmentscenarios in terms of sewer network management.
During the last few decades, Iraq faced extreme climate events represented as severe drought recorded between 2007 and 2009 followed by heavy rainfall oc- curred in a few months in southern parts of Iraq with almost two times of nor- mal records . Admo et al.  applied six General Circulation Models (GCMs) in SWAT model to investigate the impact of climate change on waterresources of Tigris River under three scenarios of future climate change which are A2, A1B and B1 of highest, medium and lowest. They summarized that the precipitation will decrease in overall five tributaries (Khabour, Greater Zab, Lesser Zab, Adhaim and Diyala) of Tigris River Basin, at the same time meaning the surface and ground water will decrease as the reflection of increasing temperature and decreasing in precipitation. It is recommended to investigat the impact of climate change for each tributary alone. Abbas et al.  used SWAT to quantify the impact of cli- mate change in Lesser Zab River, they indicated that the blue water will decrease by the range from 8% to 43% in 2046. In addition, the green water will decrease by 5% to 24% in 2046 under A1B scenario. Abbas et al.  explored the rela- tionship between climate change and its impact on waterresources of Tigris River tributaries using SWAT model. The results showed that the precipitation will be reduced by 12.6% and 21% in the period from 2049 to 2069 and distant the period from 2080 to 2099 futures, respectively under RCP8.5. Consequently, the blue water will decreases by 22.6% and 40% under RCP8.5, 25.8% and 46% under RCP4.5, and 34.4% and 31% under RCP2.6 during the periods from 2049 to 2069 and 2080 to 2099, respectively. Ali et al.  used Sen’s slope and the Mann-Kendall test to assess the streamflow trend of Lesser Zab River for the pe- riod 1964 to 2013. They indicated that stream flow would decrease by 5.09 m 3 /month in April and 1.06 m 3 /month in November with annual rate of de-
1(a)). The Boise River originates from the three forks of the Sawtooth Range that subsequently join together at the Arrowrock Reservoir to form the mainstream flowing west through the Snake River Plain that finally merges with the Snake River at Parma. Topography has west to east gradient, exceeding 3000 m at the Sawtooth Range and low elevation of 640 m feet in the western part near Parma. The basin receives precipitation in the wintertime and the spring snowmelt-induced runoff, which begins in the lower elevations around March, typically continues to contribute a significant amount of streamflow from the high mountains into July. The peak flow period is followed by a relatively dry warm summer. During the fall season, due to reduced transpiration and autumn rainfall as well as the groundwater contribution to baseflow, the streamflow increases slightly. The average annual precipitation in the basin is 661mm and average annual mean temperature is 5.9°C. The land cover in this area is highly diverse, including alpine canyons, forest, rangeland, agriculture land and urban area (Figure 2(a)). The eastern part of the basin (upstream of Lucky Peak Dam) is mainly covered by forests. The lower part of the river basin is covered by grassland, cultivated crops and developed urban areas.
a dual statutory water management goal: ‘‘to maintain a safe-yield condition in the active management area and to prevent local water tables from experiencing long term declines.’’ The term safe yield is deﬁned in the statute as a ‘‘water management goal which attempts to achieve and thereafter maintain a long-term balance between the annual amount of groundwater withdrawn in an AMA and the annual amount of natural and artiﬁcial recharge in an AMA.’’ The Arizona Department of WaterResources (ADWR) is the regulatory agency that implements groundwater management law. Water users within AMAs are required to adhere to applicable rules for conservation and water use. These include AMA speciﬁc Assured Water Supply (AWS) rules that require long-term water resource planning for water providers serving newly developed or growing areas.
Water management is a complex problem involving population, environment, economy and policy. One way to conceptualize water management policies is to build a computer simulation model (Stave 2003; Ahmad and Simonovic 2004; Le Bars and Le Grusse 2008). Models can be used to simulate complex reality and to test theories, whilst exploring their implications and contradictions. System Dynamics (SD) offers a new way of modeling complex systems and analyzing their dynamic behavior. Over the last decade, SD has been widely applied to waterresources management on global, national and regional scales (Simonovic 1999, 2002; Ahmad and Simonovic 2004; Sehlke and Jacobson 2005; Amgad Elmahdi et al. 2007; Zhang et al. 2008). In the present study, a System Dynamic approach is proposed to understand the dynamics of the complex system of waterresources management and analyze the relative implications of regulatory policies. The Tuwei river basin, a small basin in northwest China is considered as a case study. The economy of the Tuwei river basin rose greatly from 1980 to 2005. However, recently water shortage has become a serious problem which threatens to limit further economic growth.
The data contains information on the four gauge stations along the Black Volta River namely, Lawra, Chache, Bui, and Bamboi. For each gauge station, latitude and longitude, year, month, elevation, land use, soil type, rainfall, humidity, and discharge are reported. Land use data is obtained from the land use map of Ghana in Figure 2. The lands in the Black Volta basin are mostly used for agri- culture with bush fallow food crop cultivation. Except in the dry season, where livestock owners/herdsmen migrate with their animals in search of water and feed in nearby communities, animal grazing in the basin is mostly done on free range .
Projecting future changes of streamflow in the Abby River Basin (ARB) is important for planning and proper management of the basin system. The current study conducted in five stations of the Abbay river basin, and inves- tigated the annual temperature, precipitation, and riverdischarge variability using the Innovative trend analysis method, Mann-Kendall, and Sen’s slope test estimator. The result showed a slightly increasing trend of annual preci- pitation in Assoa ( Z = 0.71), Bahir Dar ( Z = 0.13), and Gonder ( Z = 0.26) sta- tions, while a significant increasing trend was observed in Nedgo ( Z = 2.45) and Motta ( Z = 1.06) stations. Interestingly, the trend of annual temperature in Assosa ( Z = 5.88), Bahir Dar ( Z = 3.87), Gonder ( Z = 4.38), Nedgo ( Z = 4.77), and Motta ( Z = 2.85) was abruptly increased. The average mean tem- perature has increased by 0.2˚C in the past 36 years (1980 to 2016). The ex- treme high temperature was observed in the semi-dry zone of northern Ethi- opia. During the study period, a significant declining trend of the river dis- charge was recorded, and the riverdischarge was sharply decreased from 1992 onwards. The results of the current study showed annual variability of riverdischarge, precipitation, and temperature of the study area of the basin that could be used as a basis for future studies.
This review study has been conducted in Malacca State, as the sample area is concentrated adjacent and along the Malacca River. According to the geographical, Malacca State is located at South West Peninsula Malaysia with coordinate of 2°12’0”N, 102°15’0”E (Universal Transverse Mercator Service, 2015), which covers an area of 1,658 km 2 and is divided into three districts, namely Alor Gajah, Jasin, and Melaka Tengah or Malacca Central (Melaka State Government Official Portal, 2015) (Melaka State Government Official Portal, 2015). The total population of Malacca State is 830,900, which can be categorized into Malay (523,800), Chinese (210,100), India (49,400), Other Bumiputera (9,600), non-Citizen (34,900) and others (4,000) (Melaka State Government Official Portal, 2015). Since the review study is focused on the Malacca River, collecting and gathering data will only be based on two districts, which are Alor Gajah and Malacca Central (figure 1). Therefore, the focus points will be upstream river, middle stream river, and downstream river.
and road construction in China have greatly increased in the most recent decade. When constructing buildings and roads, the soil is exposed to rainfall, and a greater sediment yield can be expected. After the construction, the natural surface is paved with concrete, which decreases water infiltration and increases runoff coefficient. Over the post-TGD period, several violent earthquakes occurred in the Yangtze Basin including the 8.0 magnitude Wenchuan Earthquake that resulted in the deaths of 70 thousand people. The earthquakes generated mudslides and may have increased local sediment yields. However, in view of the basin scale of the Yangtze River, these factors are limited to small regional scales, and their compre- hensive impacts on the annual water and sediment discharges are probably very minor compared with the impacts of the aforementioned factors.
A BSTRACT : This study aims to explain the dynamics of the local climate in southwestern of Côte d'Ivoire in a context of strong human pressure and climate variability. The methodological approach, based on the use of climate data an opportunity to discuss the impact of environmental change on natural resources. Southwestern Côte d'Ivoire has suffered a sharp change in vegetation cover. Since the climate out of 1970, the region observed spatiotemporal variation of rainfall regularly changing down. She sees an emphasis on the occurrence of extreme weather events, especially in terms of temperatures. These changes have resulted in a reduction of consecutive wet months and threatening storm agriculture practice in this area.