The influence of large dams on the basin has been studied by a number of researches over the past years, notably by the African Dams Project (ADAPT) interdisciplinary group (Cohen Liechti, 2013; Mertens et al., 2013; Tilmant et al., 2010), from which this study stems. In fact, several of the existing dams in the ZRB have recently, or will in the future, be subject to hydropower production capacity increases and, consequently, be driven to review operation practices. In parallel, a number of new schemes are planned, both having the capacity to modify the runoff patterns of downstream areas. Notwithstanding, despite the efforts of governments, non-government organizations (e.g. Beilfuss and Brown, 2006; King and Brown, 2014), and the permanent establishment of the Zambezi Watercourse Commission (ZAMCOM), a consensus is yet to be achieved on the equilibrium between hydropower production and environmental concerns, namely in the form of prescriptions for environmental flows. With the goal of assessing the effects of different dam operations on downstream flow characteristics, the present contribution employs a daily flow routing model in order to evaluate the impacts of different futurehydropowerdevelopmentscenarios on the ZambeziRiverbasin. Resorting to it and a multi- objective optimization technique the trade-offs between environmental and hydropower production concerns were clearly identified.
The Krishna riverbasin, 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 water resources of the Krishna riverbasin. 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 riverbasin under future climate scenarions (CMIP5 models with RCP 4.5 and 8.5 scenarios).
Abstract: Climatic variations caused by the excessive emission of greenhouse gases are likely to change the patterns of precipitation, runoff processes, and water storage of river basins. Various studies have been conducted based on precipitation outputs of the global scale climatic models under different emission scenarios. However, there is a limitation in regional- and local-scale hydrological analysis on extreme floods with the combined application of high-resolution atmospheric general circulation models’ (AGCM) outputs and physically-based hydrological models (PBHM). This study has taken an effort to overcome that limitation in hydrological analysis. The present and future precipitation, river runoff, and inundation distributions for the Lower Mekong Basin (LMB) were analyzed to understand hydrological changes in the LMB under the RCP8.5 scenario. The downstream area beyond the Kratie gauging station, located in the Cambodia and Vietnam flood plains was considered as the LMB in this study. The bias-corrected precipitation outputs of the Japan Meteorological Research Institute atmospheric general circulation model (MRI-AGCM3.2S) with 20 km horizontal resolution were utilized as the precipitation inputs for basin-scale hydrological simulations. The present climate (1979–2003) was represented by the AMIP-type simulations while the future (2075–2099) climatic conditions were obtained based on the RCP8.5 greenhouse gas scenario. The entire hydrological system of the Mekong basin was modelled by the block-wise TOPMODEL (BTOP) hydrological model with 20 km resolution, while the LMB area was modelled by the rainfall-runoff-inundation (RRI) model with 2 km resolution, specifically to analyze floods under the aforementioned climatic conditions. The comparison of present and futureriver runoffs, inundation distributions and inundation volume changes were the outcomes of the study, which can be supportive information for the LMB flood management, water policy, and water resources development.
Model uncertainty refers to the uncertainty associated with the choice of model or with underlying assumptions. This is also known as “between model” uncertainty. The usual way to communicate this uncertainty is to display the results of alternative models or sets of assumptions. For example, the global climate change community supports the development of multiple global climate models, and a rigorous inter-comparison of model results has helped to communicate between model uncertainty. In the case of the BDP2, these assumptions have to do with a broad range of assumptions, including alternative models of what is meant by “development” (Costanza 2008). The conventional model of development emphasizes economic growth and does not worry much about the distribution of the benefits of that growth. An alternative model emphasizes quality of life and sustainable well-being more broadly defined and worries more about the influence of the distribution of benefits on this well-being and the contribution of nonmarket services like those from natural and social capital. One way to express this uncertainty is by using a broad set of futurescenarios that embody this range of models. The BDP2 used scenario analysis, but only a limited range of scenarios that were variations around a single model, as BDP scenarios were created by combining current plans of LMB governments at different points in the future (2015, 2030, 2060), rather than the common scenario process of creating a full envelope of possible development alternatives. (The BDP scenarios are described in a later section). Hence, BDP2 was more a parameter sensitivity analysis as discussed above than a model uncertainty analysis.
countries, constitutes a highly complex system. With several large dams, namely Kariba, Cahora Bassa, Kafue Gorge and Itezhi-Tezhi, the basin’s hydrology is also influenced by vast wetlands with high ecological value such as the Barotse plains, the Mana Pools or the Kafue flats. The African DAms ProjecT (ADAPT) is an interdisciplinary research project aiming to develop an integrated set of methods that help assessing the ecological and socio-economic effects of dams. A comprehensive evaluation and characterization of the flow regimes before and after the dam’s construction is a stepping stone towards this goal. The analysis is based on historical data, taking into account the evolution of existing reservoirs and hydropower plants. Three indicators are considered to describe the flow regimes in the basin. They allow quantifying the seasonal transfer of the water, the sub- weekly flow fluctuations and the intensity and frequency of the flow changes. In a further stage, a semi-distributed conceptual hydrological model will be built to simulate the flow regime with and without dams for actual and future hydrological scenarios.
From a planning perspective, we compared possible scenarios of hydropowerdevelopment (as combinations of projects) that meet expected national expansion goals for 2050. In the case of the MRB, our analysis shows that baseline hydropower conditions have already significantly altered multiple basin-level processes vital to the health of the Mompós wetlands floodplains – in particular, loss of longitudinal connectivity of spawning habitats of migratory fish ( − 54.8 %) and decreased sediment transport ( − 39 %) – while flow regime and wetland hydrological variability main- tain near natural conditions. Developmentscenarios, how- ever, show a potential range of up to one order of magni- tude of additional impacts across comparable hydropower capacity. Some futuredevelopmentscenarios can result in significant physical or hydrologic alteration, i.e., a loss of longitudinal connectivity to virtually all remaining spawning habitat for migratory fish and significant reductions of sed- iment loads, while substantially altering floodplain (lateral) seasonal inundation dynamics in extensive areas of the Mom- pós Depression. Our analysis of possible scenarios, however, indicates that other scenarios would result in much lower dif- ferential changes. This emphasizes the need for comprehen- sive basin-level approaches to water infrastructure planning that integrate broader environmental and cumulative impacts
groups (e.g., private developers, governments, local communities, fishing households, farming households, consumers, etc.) as well as the impact on poverty within LMB countries. Also, there is mounting evidence that a skewed income distribution is highly correlated with a range of social problems and reduced quality of life for both the rich and the poor (Wilkenson and Pickett 2009). How the future is discounted is a key issue in any analysis of projects with long time horizons. Ideas about discounting are rapidly evolving and changing, but there is growing agreement that simply discounting every- thing at the same, constant exponential rate is too simplistic. Some alternatives to standard discounting were explored and a sensitivity analysis showed that varying the discount rate could have dramatic effects on the estimated net social benefits. Even in our worst-case scenario in the sensitivity analysis, however, the ben- efits of hydropower are still positive for Lao PDR, while they may be negative for other countries. As one potential solution, policy-makers can implement a form of ‘‘payment for ecosystem services’’ to Lao PDR (from the other countries in the LMB as well as elsewhere) larger than the foregone benefits from dam construction. Something similar has been proposed by Ecuador in return for leaving major Amazonian oil reserves in the ground and in Indonesia for protection of native forests. • Develop a more thorough assessment of the value of direct and indirect ecosystem services This includes the full range of services from provisioning services like capture fisheries to the broad range of regulatory and cultural services provided by wetlands and other natural ecosystems. Our analysis showed that varying the assumptions about the value of capture fisheries and wetlands can make a significant difference in the evaluation of the net benefits of futurescenarios, even changing the sign in many cases. Ecosystem services are becoming an important way of understanding, valuing, and managing our environmental assets and a more direct and concerted effort to understand, model, and value ecosystem services should be a major part of the next BDP phase. This could include a review, survey, and classification of aquatic habitats in terms of biodi- versity and ecological importance, prioritization of key tributaries for ecosystem integrity and health of the Mekong, highlighting those affected by proposed main- stream dams, assessment of the ecological importance and productivity of the seasonally exposed in-channel wetlands, and assessment of the possibilities for river based ecotourism. In addition, impacts of developments on indirect ecosystem services of the Mekong—both negative (e.g., loss of provisioning, regulating, and cultural services of the river) and positive (e.g., the multiplier effect of hydropower benefits)—should be
Water storage systems have been established to achieve many goals. Conducting periodical assessments of these systems is necessary to improve their performance, as a result of population growth and the expansion of the water supply projects that belong to the municipality as well the development or creation of irrigation projects that derive their water from the storage systems (Jothiprakash and Shanthi, 2006), (Sattari et al, 2009), (Khan et al, 2012), in addition to adapt to the effects of climate change (Fayaed et al, 2013). The performance of water storage systems should be re-assessed to discover new rules of improvement and to consider the possible addition of new storage units. These improvements can be achieved through the identification of new optimal operation policies. New software and techniques can be used to calculate the highest benefit while considering all the restrictions imposed by the new system structure. These new developments were applied to the Mosul and Dokan reservoirs. Identifying new operational policies for storage system performance of the Bekhma and Makhoul reservoirs under different scenarios is necessary because they will be added to the storage system consists of Mosul and Dukan reservoirs.
these high altitude mountain ranges of the Jhelum River catchment. The most active hydrological areas, which generate the greatest amount of water for the Mangla Basin, are ungauged or scarcely gauged, particularly at elevations greater than 3000 m. Hydrometeorological studies are essential in this hydrologically vigorous area at altitudes greater than 3000 m, where the greatest amount of precipitation falls in solid form. Remote sensing tools are a suitable approach to investigate cryosphere dynamics efficiently in these inaccessible highlands. An understanding of cryosphere dynamics and its impact on the hydrological behaviour of the sub-basins of Mangla catchment is vital for better water resources management in Pakistan. In this section, the investigation focuses on studying the snow cover dynamics in Mangla catchment by using a freely available remote sensing snow cover data product and the climate and hydrological gauge data of stations located within or close to the catchment border (at different elevations). Moreover, the precipitation data plays a tremendously important role for the hydrological analysis. During the last decade, the use of remote sensing precipitation data has been considered the most reliable source for estimating the hydrological regime in ungauged or scarcely gauged catchments in high altitude mountainous areas.
Our simulations under climate change scenarios show a range of −14% to +10% for mean annual Zambezi discharge at Tete in the near future (2021–2050 as compared to Baseline simulation 1961–1990). These results (and the large uncertainty) have to be interpreted within the context of the results of previous studies. Harrison and Whittington (2002) focussed on the upper ZambeziRiver at Victoria Falls. For the 2080s their three climate scenarios show a warming of about +5 ◦ C and a reduction in rainfall between −2% and −18%, which results in a reduction in runoff by −10% to −36%. In a preliminary analysis the World Bank (2010) used GCM data (A1B emission scenario) for the whole Zambezi region. For 2030 they estimate a change in runoff between −13% and −34% (depending on the sub-region). Beilfuss (2012) summarized existing climate change assessments for the Zambezi and concludes that by 2050 runoff is likely to decrease by −26% to −40% if the reduc- tion in rainfall lies between −10% and −15%. This corresponds well to our climate sensitivity tests where for a reduction of −10% in rainfall the simulation shows a reduction of −32% in discharge. However, apart from these dramatic projections with reduction in ﬂows we also have to acknowledge that rainfall may actually increase in the future, highlighting the uncertainty in the climate model scenarios.
In this study, we represented changes in land use using both an idealized scenario for 2030, in which the official Jakarta Spatial Plan 2030 is fully implemented, and a simple extrapolation of past increases in flood risk due to land use change to the future. Our results show that under the ideal- ized scenario (land use change alone), risk would decrease by 12 %, compared to an increase of 45 % using the extrapola- tion of past trends to the future. Whilst we acknowledge that these should only be considered as first order estimates, these large differences do indicate the large potential of land use planning to mitigate flood risk, especially when combined with other measures. The results for the idealized land use scenario are particularly encouraging, if the plan can be suc- cessfully implemented, given the fact that changes in expo- sure through urban development are seen as one of the main drivers of risk in developing countries (Jongman et al., 2012; UNISDR, 2013). Moreover, the land use plan scenario does not include assumptions on potential measures or strategies that could be taken to further reduce flood risk. For exam- ple, in Indonesia as a whole, Muis et al. (2015) simulated increases in both river and coastal flood risk by 2030, as- suming a scenario where building is allowed in flood-prone areas, and several scenarios where new buildings are prohib- ited (with different levels of enforcement) in the 100-year flood zone. They found that river flood risk could be reduced by about 30–60 %, and coastal flood risk by about 65–80 %, compared to the scenario in 2030 with no building restric- tions in the flood-prone zone.
In many river basins the performance of operational hy- drological modeling and forecasting is limited because in situ observations of precipitation and river discharge are scarce or unavailable. This is also the case for many of Africa’s large river basins which are poorly gauged (e.g., Zambezi, Volta, Congo). Consistent, long-term and spatially resolved in situ observations of precipitation and river discharge are unavail- able for large portions of Africa. Moreover, the number of operational meteorological stations and river discharge sta- tions has been decreasing consistently around the world since the 1970s (Fekete and Voeroesmarty, 2007; Peterson and Vose, 1997). Remote sensing techniques have the potential to fill critical data gaps in the observation of the global hydro- logical cycle. All major components of the water balance, ex- cept river discharge, can now be estimated based on various types of remote sensing data. However, the available tech- niques are still limited by coarse spatial and temporal reso- lution as well as large and/or poorly understood error char- acteristics (Tang et al., 2009). From a management perspec- tive one of the most important components of the hydrolog- ical cycle is river discharge. Extremely high flows in rivers cause flooding which can have severe consequences in terms of fatalities and economic damage. Low flows cause con- flicts in the allocation of scarce water resources between eco- nomic sectors and/or the environment. Therefore, in many river basins there is a need for hydrological models to provide operational estimates of river discharge based on remotely sensed observations and limited available in situ measure- ments.
The Akosombo reservoir is fed by numerous tributary rivers to the Volta River, all of which rain-fed. The volume of water in the reservoir swells up during the rainy season and shrinks during the dry season. There is a large inflow of water into the reservoir in August during the peak rainfaill period and the reservoir attains its highest level in August/September. Spillage is always carried out in September mostly when the level of the Volta Lake rises above 84.3 m.a.s.l. However, the water level in the reservoir starts falling in October/November, with the onset of the harmattan (a dry and dusty northeasterly trade wind which blows from the Sahara Desert over the West Africa into the Gulf of Guinea between November–March) in the catchment area, and generally reaches its lowest level in May/July annually. Generally, the Akosombo Dam has experienced consistent reduction of water inflow into the reservoir mostly due to low rainfall patterns and high temperatures over the past years, and this has led to the occasional shut down of the turbines . Therefore, discharge from the Akosombo Dam varies and depends on the amount of water inflow into the reservoir. However, other factors such as temperature also account for discharge at the dam.
During this consultation, mobilising the key stakeholders through the RMBs will be pivotal in putting pressure on the power company to change its strategy (Haller & Chabwela, 2009), although a positive outcome has yet to be realised. Further actions can also orientate around highlighting the impact of hydropower on loss of livelihoods and food and nutritional security, which could ultimately result in increased poverty and hunger, contrary to addressing the Sustainable Development Goals, especially SDG 1 alleviating poverty (Lynch et al. 20917). This is particularly important because poverty is widespread in Zambia, especially in rural communities such as those occupying the Kafue Flats floodplain. The problem of food security and poverty is expressed through dependency on fisheries and the lack of viable and sustainable livelihood options. Fishing communities suffer the threat of poverty and food security because of declining catches and floods that damage crops. Much of their food comes from the fishery and fish-dependent households have little or no alternative livelihoods. The population in the Kafue Flats floodplain is especially dependent on fish availability, and the seasonality of the activity implies vulnerability to food security during certain periods of the year. Consequently, it is likely that any adverse changes to the flooding dynamics with impact on rural livelihoods and food security of the communities dependent on the fisheries and wildlife resources in the region as well as disrupt recession agricultural practices. Unfortunately, there are few alternatives for the indigenous tribal people of the Flats so such a scenario will lead to considerable social disruption.
The Plata RiverBasin is a developing riverbasin and each country member has distinct water related demands and requirements. Equally, each of the countries imposes pressures on the water environment and often on other countries in competition for river resources, including fishery resources. An agreement, which forms the Treaty of the La Plata Basin, was rat- ified by the five national states and remains in force. The main constraints to unified development and man- agement are political. Sustainable development makes it unrealistic to consider any country in isolation and it is very necessary to be aware of country needs and impositions on basin resources in order to integrate them within the framework of a feasible multi-purpose basin management plan and to adapt this to progressive changes. The Plata Basin is not a heavily populated riverbasin, with population density of approximately 35 people per square kilometre. Detrimental impact on fisheries, therefore, would be expected to be more related to the industrial and agricultural development using environmentally unfriendly practices, rather than the present population density and fishing pressure. It has been reported that contamination of fish with toxi- cants commonly used in industry and agriculture has been on the increase during the last decade. There has been also an increase in the number of conflicts among artisanal, commercial and recreational fishers (Quiros 1993).
Notwithstanding the important longterm challenges of finding water for environmental restoration and for some Indian communities with unresolved water rights claims, in most other respects, this tradition of full use is not inherently problematic, as long as the least reli able component of water yield is only used as a supplemental supply (ideally for lowvalued uses) and not as the baseline supply supporting urban growth. Unfortunately, this is not the situation in many pockets of the basin, as rural uses generally precede urban uses (and thus rank higher within states’ priorappropriation systems). This is an unusual situation, but it is one that can be remedied. As noted above, state water laws provide an important mecha nism to reallocate water (and the risk of short ages) through voluntary agricultural to urban water transfers, ranging in form from the dozens of small transactions occurring each year along Colorado’s Front Range to the massive deals in southern California that have weaned urban areas off surplus flows (i.e. flows in excess of the state’s apportionment) through complex conservation and transfer arrange ments with major irrigation districts. But, ulti mately, the efficacy of this strategy for managing water supply risk in particular locales in the Colorado Riverbasin is shaped and limited by the larger interstate rules of water allocation codified in the Law of the River and, perhaps more importantly, by the realization that the overarching challenge in the basin is to acknowledge and live within the limits of the river. This challenge has a particularly complex flavour in the Colorado Riverbasin due to the river’s overallocation.
calculated. For the year 2015 that the study was conducted in the irrigation scheme, ir- rigation water used in unit area (ha) amount, net irrigation water requirements of plants, irrigation rate, irrigation efficiencies, total irrigation water used in the scheme, the total production value and average production values belonging to the irrigation schemes is given in Table 3. Settlement system and position of irrigation schemes op- erated according to the principle of integrated riverbasin management are arranged from downstream to upstream in the basin. Water, returning from an irrigation scheme is the water source of the other scheme. Total net irrigation area of 16 irrigation schemes operated in the basin is 166,381 hectares; total irrigated area is calculated as 141,449 hectares. Approximately 85% of net irrigation area is irrigated virtually. Irriga- tion water used unit area (ha) varies 3380 to 14,607 m 3 ∙ha −1 in the basin irrigation
The basic approach of dynamical downscaling via RCMs follows the same procedures established for GCMs, in terms of physically-based governing equations, but over a smaller scale in both time and space. GCMs evaluate climate variables over the entire globe over a multi-decade time scale, whereas RCMs focus on a regional area, on the order of a continent or single ocean body, over a more modest temporal scale, on the order of a few months or years, for analysis. Experimentation with such an approach started in the late 80s and were later summarized by McGregor (1997). A fundamental assumption of regional modeling approaches is that, over a limited area, data on large- scale climate variables can be used as initial (or driving) conditions to a RCM. The focus on a smaller domain size within the model negates the need for additional computational requirements that are often impractical.
Due to the fact that an important amount of the grants that will be given to our country from the EU Structural Funds will be allocated to those projects with local and regional characteristics, since April 2002, a joint SWOT analysis has been carried out by the representatives of the SPO and the EU with the participation of local ac- tors, and a regional vision has been formed by identifying the priorities of the prov- inces and the measures related with them. Regional Development Program in Sam- sun, Kastamonu and Erzurum NUTS II Regions ( RD-SKE NUTS II Regions) , of which the SPO is the beneficiary, has been initiated first in our region as a pilot pro- gram and Yesilirmak RiverBasinDevelopment Union, whose centre is in Amasya, has taken the role of the coordinating agency in the implementation of the program in the region.