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Low Threshold Safety Assessment for Small Dams
Abstract
This study examines the various structural and geotechnical conditions of small dam facilities in the Dresden Basin and its surroundings, specifically in relation to the significant flood danger posed by the Elbe River. In order to maintain the resilience of the Dresden basin against flood occurrences, it is imperative to enhance dam safety and efficient operation of these small dams, which play a vital role as essential infrastructure for flood protection. The main goal of this research is to evaluate the existing condition of these dams through a dam questionnaire and propose possible safety enhancements that might reduce the danger of flooding in the area. The study was carried out using a mix of field surveys and expert dis-cussions, with the main objective of identifying the locations that are most susceptible to flood-induced damage. The report emphasises significant issues, including deficiencies like in the structure of current dams, insufficient flood control systems, and the need for improved maintenance procedures. Moreover, the research identifies certain areas inside the Dresden basin that are most prone to floods, requiring urgent action. The results emphasise the need for strengthening small dams as a precautionary step against flooding, particularly considering the frequent and intense flooding incidents in the region. Suggested measures include of enhancing dam infrastructure and dam environment development. Finally, Analytical Hierarchy Process is suggested as the potential method towards finding the weighting of the dam safety factors. The research seeks to solve dam safety challenges to make Dresden Basin and its neighbouring areas safer and more robust to flood management.
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Tailings dam failures may cause catastrophic losses of personnel and property as well as environmental pollution. Therefore, the accurate assessment of the risks of tailings dams and the implementation of effective control measures are critical to ensuring the safety and stability of tailings dams. In this study, first, based on the Decision-Making Trial and Evaluation Laboratory and interpretive structural modeling (DEMATEL-ISM), a causal coupling hierarchical structure model of the disaster-causing factors of tailings dams was established. The importance and causal relationships among the disaster-causing factors were analyzed, and the key disaster-causing factors and total degree were identified. Second, according to the hierarchical structure model, the Pythagorean fuzzy analytic hierarchy process was utilized to calculate the hierarchical weights of the factors. According to DEMATEL and complex network analysis, the centrality and clustering coefficient of each disaster-causing factor are obtained. A model for determining the weights of disaster-causing factors is proposed with centrality (α), hierarchical weight (β) and clustering coefficient (θ) as the core. This model reflects not only the importance of each disaster-causing factor to the risk of tailings dam failure but also the causal coupling relationship between the factors and the structural importance of each factor in the tailings dam system. Finally, combined with the cloud model and matter-element extension model, a risk assessment model for tailings dam failure was proposed. An example of a tailings dam in China was analyzed. The results show that the case risk assessment results are consistent with the actual project assessment results. The weight determination and risk assessment method reduce the impact on the accuracy of risk assessment results due to the ambiguity, randomness and correlation of disaster-causing factors.
In this research, walking facilities and scopes for improvement of a major urban arterial of Dhaka city has been investigated. In order to ensure Progati Sarani as an ideal walkable area, walkability needs to be enhanced as walking is an essential and effective medium of sustainable urban transport. The supreme aim of this research is to determine the walkability indices of these particular areas and to find appropriate pedestrian safety measures for the sake of better and safe environment for pedestrians. A short field survey and a brief questionnaire survey were carried out for the completion of this study. The research identifies the most vulnerable areas for pedestrians in commercial areas of eastern part of Dhaka city. Notable hazards are roadway obstructions, road infrastructure deficiency, crossing facilities, motorists behaviours, safety and security etc. Finally, the overall walkability index has been calculated which is found to be approximately 38.8 out of total 100, considered as less walkable. This result is not satisfactory if it is compared to other major Asian cities. However, a huge volume of pedestrian movement is observed in the study area, most of whom are working class people and students. In such a situation, efforts should be given in formulating policies to promote walking as a priority mode of sustainable transportation system. Achieving a safe and congenial environment by incorporating road environmental safety measures along with road user's behavioural improvement is fundamentally important for the betterment of all sorts of pedestrians, particularly for ensuring their legitimacy and safety.
In this study, a relation-based dam suitability analysis (RDSA) technique is developed to identify the most suitable sites for dams. The methodology focused on a group of the most important parameters/indicators (stream order, terrain roughness index, slope, multiresolution valley bottom flatness index, closed depression, valley depth, and downslope gradient difference) and their relation to the dam wall and reservoir suitability. Quantitative assessment results in an elevation-area-capacity (EAC) curve substantiating the capacity determination of selected sites. The methodology also incorporates the estimation of soil erosion (SE) using the Revised Universal Soil Loss Equation (RUSLE) model and sediment yield at the selected dam sites. The RDSA technique identifies two suitable dam sites (A and B) with a maximum collective capacity of approximately 1202 million m3. The RDSA technique was validated with the existing dam, Gomal-Zam, in the north of Sanghar catchment, where RDSA classified the Gomal-Zam Dam in a very high suitability class. The SE estimates show an average of 75 t-ha−1y−1 of soil loss occurs in the study area. The result shows approximately 298,073 and 318,000 tons of annual average sediment yield (SY) will feed the dam A and B respectively. The SE-based sediment yield substantiates the approximate life of Dam-A and Dam-B to be 87 and 90 years, respectively. The approach is dynamic and can be applied for any other location globally for dam site selection and SE estimation.
Small dams managed by local governments in the Republic of Korea are facing operational difficulties owing to problems such as a decrease in the long-term storage capacity because of sedimentation and leakage, acceleration of aging, rapid lowering of water levels with seasonal rainfall and water usage, and the resulting deterioration of the overall integrity. However, the public demand for small dams has increased sharply for various purposes, especially flood and drought control. This paper presents a developed model for evaluating the condition of small dams using an analytic hierarchy process. Seventy-five earth dams in a province located in the eastern part of the Korean Peninsula were chosen. Three major components of dams, i.e., embankments, spillways, and water intake facilities, as well as the overall condition of the dam system, were evaluated. The usefulness of the improved model and its differences from the existing method were verified using the t -test. The improved model was found to be relatively simple and easy to apply in practice, and it enables on-time action for further treatment or reinforcement.
This study attempted to delineate and map potential groundwater recharge zones of the Singida, semi-arid, fractured crystalline basement aquifer using open source remote sensing and GIS software. Various thematic maps such as lithology/hydrogeology, soil, land-cover/use, slope, lineament density, drainage density and rainfall distribution were integrated in QGIS software. Vector input layers were rasterized and resampled using QGIS wrap projection function to make sure that the grid cells are of the same size. Reclassification using SAGA and GRASS reclass algorithms in QGIS was carried out to realign the factor classes in a consistent scale, and reclassification to a scale of 1 to 5 was carried out to harmonize the results. The study identified a number of potential areas for groundwater recharge, groundwater exploration, groundwater development and potential areas for artificial groundwater recharge. Potential groundwater recharge zones for the Singida semi-arid fractured aquifer are restricted to areas with high lineament density, cultivated areas, grassland and flat to gentle slopes. The potential of groundwater recharge is also observed in areas with low drainage density. The delineated zones provide a good understanding of the potential recharge zones, which are a starting point for recharge zone protection. This blended approach can be utilized for carrying out suitability analysis using the weighted overlay analysis approach. Areas designated good and very good are recommended for artificial recharging structures as an alternative technique for enhancing groundwater recharge through rainwater harvesting. This will help to augment groundwater storage in this semi-arid environment.
Dams provide a water supply, irrigation and power generation. However, the economic, social and environmental impacts are serious when they rupture. It is important that dams continue to function properly and are constantly evaluated for their safety and functionality. Contrary to general belief, small dams are the ones that present the most problems, because they are often built without adequate design and construction methods. One of the methods to evaluate the safety of a dam is through the Dam Safety Index (DSI), which may not entirely avoid subjectivity in dam safety assessment but does propose balanced individual subjectivities in determining the weights of the index criteria. The DSI can also assist managers with preventive maintenance schedules in a dam safety assessment. This work aims to reassess the importance of the parameters of the DSI based on a new weighting of these criteria. The modification of the DSI shows a new bias in the weighting of the criteria that composes the index, not only considering technical aspects, but also legal and environmental ones.
Significance
North American and European countries built many large dams until 1975, after which both started to abandon a significant part of their installed hydropower because of the negative social and environmental impacts. However, there has been a recent trend of new large hydropower dams being built in developing countries, particularly in megabiodiversity river basins, such as the Amazon, the Congo, and the Mekong. The socioeconomic and environmental damages in these river systems are even greater than the early costs in North America and Europe. This paper discusses how the hydropower sector needs to not only focus on energy production but also, include the negative social and environmental externalities caused by dams and recognize the unsustainability of current common practices.
The last 60 years has seen unprecedented groundwater extraction and overdraft as well as development of new technologies for water treatment that together drive the advance in intentional groundwater replenishment known as managed aquifer recharge (MAR). This paper is the first known attempt to quantify the volume of MAR at global scale, and to illustrate the advancement of all the major types of MAR and relate these to research and regulatory advancements. Faced with changing climate and rising intensity of climate extremes, MAR is an increasingly important water management strategy, alongside demand management, to maintain, enhance and secure stressed groundwater systems and to protect and improve water quality. During this time, scientific research—on hydraulic design of facilities, tracer studies, managing clogging, recovery efficiency and water quality changes in aquifers—has underpinned practical improvements in MAR and has had broader benefits in hydrogeology. Recharge wells have greatly accelerated recharge, particularly in urban areas and for mine water management. In recent years, research into governance, operating practices, reliability, economics, risk assessment and public acceptance of MAR has been undertaken. Since the 1960s, implementation of MAR has accelerated at a rate of 5%/year, but is not keeping pace with increasing groundwater extraction. Currently, MAR has reached an estimated 10 km³/year, ~2.4% of groundwater extraction in countries reporting MAR (or ~1.0% of global groundwater extraction). MAR is likely to exceed 10% of global extraction, based on experience where MAR is more advanced, to sustain quantity, reliability and quality of water supplies.
Small scale irrigation farming has been recognized as an important avenue for improving the well being of poor people living in arid and marginal areas of the world. The contribution of small scale irrigation can be seen in its ability to ensure food security as well as contribute to the income of farmers. In the Garu-Tempane District, small scale irrigation farming is a major source of livelihood for people in the district. Despite the importance of the irrigation schemes to dry season farming the schemes face challenges such as inadequate water, inadequate canals, choked and broken canals due to frequent breakdown and inadequate repairs which affect their effective operation. Although the major use of the dam waters was dry season farming, animal watering and fishing were also found to be significant uses of the dam waters. In north-eastern Ghana as it is in many parts of the third world, external development agencies support the formation of Water User Associations (WUAs) for the management of community-based irrigation schemes. Although, the management of the schemes and the use of the dam is the responsibility of the community represented by the WUAs it was revealed by the study that, in the management of challenges that confront small scale irrigation schemes, WUAs depended on the supportive roles of traditional authorities as well as district assemblies for discharging their management responsibilities more effectively.
Longitudinal connectivity is a fundamental characteristic of rivers that can be disrupted by natural and anthropogenic processes. Dams are significant disruptions to streams. Over 2,000,000 low-head dams (<7.6 m high) fragment United States rivers. Despite potential adverse impacts of these ubiquitous disturbances, the spatial impacts of low-head dams on geomorphology and ecology are largely untested. Progress for research and conservation is impaired by not knowing the magnitude of low-head dam impacts. Based on the geomorphic literature, we refined a methodology that allowed us to quantify the spatial extent of low-head dam impacts (herein dam footprint), assessed variation in dam footprints across low-head dams within a river network, and identified select aspects of the context of this variation. Wetted width, depth, and substrate size distributions upstream and downstream of six low-head dams within the Upper Neosho River, Kansas, United States of America were measured. Total dam footprints averaged 7.9 km (3.0–15.3 km) or 287 wetted widths (136–437 wetted widths). Estimates included both upstream (mean: 6.7 km or 243 wetted widths) and downstream footprints (mean: 1.2 km or 44 wetted widths). Altogether the six low-head dams impacted 47.3 km (about 17%) of the mainstem in the river network. Despite differences in age, size, location, and primary function, the sizes of geomorphic footprints of individual low-head dams in the Upper Neosho river network were relatively similar. The number of upstream dams and distance to upstream dams, but not dam height, affected the spatial extent of dam footprints. In summary, ubiquitous low-head dams individually and cumulatively altered lotic ecosystems. Both characteristics of individual dams and the context of neighboring dams affected low-head dam impacts within the river network. For these reasons, low-head dams require a different, more integrative, approach for research and management than the individualistic approach that has been applied to larger dams.
The water scarcity issues are increasing through out the world. Pakistan is also facing water
crises and its water demands are increasing every day. During this research it is investigated that
small dams are playing an important role for the sustainability of groundwater and agriculture. The
main objective of this study was to assess the environmental impacts of small dam on agricultural and
ground water. Proper planning and management of small dams may improve the sustainable
agriculture in Pakistan. It is also concluded that small dams are significantly contributing towards
economy, environment, local climate, recreational activities and crop production. Small dams can
also be utilized for the production of electricity at local level. On the other hand, water management
issues can be resolved by the involvement of local farmer’s associations. Water losses through
seepage, unlined channels and old irrigational methods are most critical in developing world.
Considering the overall positive environmental impacts, construction of small dams must be
promoted.
In Germany the technical rules for dams and reservoirs are published in the standard DIN 19700 Part 11 and 12. A classification into large, medium, small and very small basins is made, to enable owners, operators, consultants, contractors and authorities to assess appropriate analysis as well as operation rules to the works of different size and risk level. Uncertainty often exists in practice how to deal with small plants. In the realization of the regulations it is often necessary to take into account the above two parts of the standard. Allowable simplifications are often not described or not specified detailed enough. Therefore the DWA (German Association for Water Management, Waste Water and Waste) has decided to elaborate and publish a technical bulletin about the planning, construction and operation of small plants. This guideline is numbered M 522 and will be entitled "Small Dams and small Flood Control Reservoirs". This paper covers the most important points of the upcoming guideline. These are the calculation of the hydrological parameters, the safety and stability of these small dams as well as the construction, the appurtenant works and the consideration of ecological aspects.
Groundwater depletion poses a significant threat in arid and semi-arid areas where rivers are usually ephemeral and groundwater is the major source of water. The present study investigated whether an effective water resources management strategy, capable of minimizing evaporative water losses and groundwater depletion while providing water for expanded agricultural activities, can be achieved through aquifer storage and recovery (ASR) implemented in conjunction with water storage in an ephemeral river. A regional development modeling framework, including both ASR and a dam design developed through system dynamics modeling, was validated using a case study for the Sirik region of Iran. The system dynamics model of groundwater flow and the comprehensive system dynamics model developed in this study showed that ASR was a beneficial strategy for the region’s farmers and the groundwater system, since the rate of groundwater depletion declined significantly (from 14.5 meters per 40 years to three meters over the same period). Furthermore, evaporation from the reservoir decreased by 50 million cubic meters over the simulation period. It was concluded that the proposed system dynamics model is an effective tool in helping to conserve water resources and reduce depletion in arid regions and semi-arid areas.
Recently, the use of multicriteria quantitative evaluation methods for solving social and economic problems has grown considerably. One of two major components of quantitative multicriteria evaluation methods strongly influencing the evaluation results is associated with the criteria weights. In practice, the criteria weights are determined in assessing the economic development of the state and its regions, the commercial activity and strategic potential of enterprises, the effectiveness of particular investment projects, etc. Several theoretical and practical methods of determining the significance (weight) of criteria by experts are known. Pairwise comparison of criteria is widely applied, and the most well‐known, widely applied and mathematically grounded technique is the so‐called Analytic Hierarchy Process (AHP). However, the application of this method is limited because of a great number of evaluation criteria, contradicting expert estimates and incompatible matrices obtained. In the present paper, the application of AHP technique to more complicated cases is considered and some algorithms are offered.
First Publish Online: 09 Jun 2011
Dam decay provides opportunity to restore degraded ecosystems. When choose an alternative to manage a dangerous dam to ensure dam safety and satisfy other human needs, ecological needs should be considered. In this paper, based on sustainable management goal, alternatives for managing a small flood control dam were assessed from improving dam safety, controlling flood and restoring riparian vegetation. Impacts on dam safety were quantified by an index integrating social influences from dam break flood inundation. Capability to control flood was assessed based on reservoir routing and hydrologic modeling. Opportunity to recover riparian vegetation was quantified by an index representing hydrologic alterations to natural flow regime. Final priority of each alternative was then obtained by multiplicative synthesis. Synthesization results indicated the decreasing dam height alternative had the highest priority to achieve the sustainable goal, because it flexibly regulated inflows for ecological considerations within the limits of flood control standard.
Water is the main limiting factor for crop production in semi-arid sub-Saharan Africa. This paper presents an evaluation of the effectiveness of community-driven smallholder irrigation schemes using micro dams under current operational practices. The research site is the semi-arid Vudee sub-catchment within the Makanya Catchment, which is part of the Pangani River Basin (Northern Tanzania). A micro dam is presented as a case study. Micro dams are popular in the study area they have water sharing system between upstream and downstream users put in place with minimum input from external agencies. The effectiveness of micro dams on dry spell mitigation is investigated. The significance of dam size, total water diverted per season, system losses and approximate amounts of water received by each farmer in a given season is analysed. Local smallholder farmers have put up the micro dams to address their need for extra water for agriculture. The capacities of the micro dams are very small but without them there is insufficient water to allocate to at least one irrigation event per farmer in a season, the dams serve a useful purpose when operated as night storage reservoirs. The study found out that the micro dam system, under current operational rules, is inefficient as the high system losses put to question the wisdom of irrigating over scattered sites as opposed to one common irrigation plot near the dam site where each participant would be allocated a small piece of land to irrigate.
In the last decades, Italy has experienced several strong earthquakes, triggering the attention on the high seismic risk associated with the potential instability of large existing earth dams. Under intense seismic events, dam response depends on various factors, among which the geometry and the type of water retention scheme. This paper explores the influence of these factors, comparing the seismic performance of two idealised earth dams: a homogeneous and a zoned one. The simplified models adopted in the analyses are representative of these two classes of earth dams, often adopted in the sixties to design various dams located in southern Italy. The idealised models, here examined in detail, have comparable heights and foundation soil conditions, differing in terms of water retention scheme. The seismic response of the dams was evaluated through time-domain non-linear dynamic analyses in which the same input ground motion, represented by real-time histories, was applied at the base of the models. It is shown that for highly inelastic systems, such as those at hand, duration of input motion should be accounted for in addition to compatibility criteria with a design elastic response spectrum. Also, different slope of dam flanks, shear strength mobilisation at the end of dam construction and high stiffness contrast at the shells-core contacts are shown to result in different deformation patterns at the end of earthquake loading. Some peculiarities in the behaviour of these classes of earth dams are highlighted in the paper, providing a guidance for the rational assessment of their seismic performance.
The hydrological alterations induced by dam construction modify natural flora and fauna habitats and impair ecosystem stability. Although many studies have documented the impacts of large dams on streamflow, few have described the effects of small dam construction on hydrological conditions. The cumulative effects of intensive small dams may also cause severe ecological problems. To evaluate the impacts of dam construction on the indicators of hydrological alterations, a framework that combined a hydrological model and the post bias correction method was proposed. The hydrological alterations of two individual rivers in the Jiulong River basin that experienced impacts from intensifying small hydropower reservoirs, the North River and the West River, were analyzed using the proposed framework. The results show that the framework can successfully avoid misleading the impacts of dam construction on monthly runoff and multi-minimum values detected by the previously common method that did not separate the impacts of climate change and dam construction on flow regime. The small hydropower-dominated North River and the flood-control-dominated West River exhibited generally consistent change patterns of unchanging monthly river discharge, reduced high pulse count, reduced rise and fall rates, and increased number of reversals. Conversely, the changes to several Indicators of Hydrologic Alterations (IHA) differed between the two rivers. The flood-control-dominated West River exhibited 1) increased indicators, such as the base flow index, multi-day minimum flow and high pulse duration and 2) decreased multi-day maximum flow and low pulse count. Unlike the West River, the hydropower-dominated North River experienced 1) increased low pulse count and 2) decreased indicators such as multi-day minimum flow and low pulse duration. Our results implied that the ecological impacts of the small hydropower-dominated North River may exceed those of the flood-control-dominated West River. Therefore, the minimum ecological water demand should be considered not only in the large reservoirs operation, but also in the operation of small hydropower reservoirs.
In Australia and other countries, small private dams in agricultural catchments pose both disastrous individual and cumulative dam failure flood threats to downstream communities; threats that can be exacerbated by increased rainfall intensities caused by climate change. This paper addresses the need for a low cost, scientifically acceptable mechanism and policy guidance to help dam owners and governments better understand and manage these risks and assure community safety. To this end an innovative, cost-effective farm dam flood safety review/design tool is developed and tested in Australia, including hydrology-diverse Tasmania, to complement best practice dam safety assurance policy. The tool's development involved generating complex catchment data to represent hydrologically homogenous regions using best practice water engineering methods, to derive simple regionalised dam flood capability prediction relationships of acceptable accuracy. Results demonstrate the tool's successful development and potential transferability to different hydrological regions; how the relationships can be refined by future research and potentially made to account for climate change; and how the tool can be applied within a best practice dam safety assurance policy which includes additional farmer-friendly elements. The findings are potentially transferable to any region to assure communities that cumulative safety threats posed by rural catchment dams are minimised.
Small dams and associated reservoirs have notable effects on soil and water dynamics in prairie streams. In this study, we developed a simulation module of small dams in the soil and water assessment tool (SWAT) to evaluate their long-term effects on stream flow and water quality at a watershed scale. To overcome the challenges in characterizing small storage and short retention time in small reservoir routing, concepts of equivalent reservoir storage and equivalent reservoir discharge are applied by which the average daily storage and daily discharge of the small reservoirs are calculated. Accordingly, the sediment deposition and nutrient abatement within the reservoir are computed using available SWAT routines. The effects of small dams in reduction of daily peak flow, sediment, and nutrient loads at the watershed outlet are obtained by summing the effects of all small dams within the watershed considering both reservoir and channel processes. The model is applied to the 74.6-km(2) South Tobacco Creek watershed located in Southern Manitoba of Canada. A total of 26 small dams exist in the watershed with surface area ranging from 0.002 to 0.492 km(2) and storage capacity from 3,380 to 642,000 m(3). The simulation results show that the combined effect of these small dams can reduce daily peak flow by 0-14% at the watershed outlet depending on climate and initial reservoir storage conditions. The estimated average annual sediment, total nitrogen and total phosphorus reductions at the watershed outlet are about 4.51, 3.59, and 2.96%, respectively. However, the on-site effects of individual small dams are much higher depending on its size, location, shape, drainage area, and land use compositions in the contribution area. The simulation results also show that snowmelt-flooding events have higher reduction amounts but lower relative reduction rates compared to rainfall storm events and the back-flood small dams have greater impact on sediment, nitrogen, and phosphorous abatement followed by multipurpose small dams and dry dams in the study watershed. (C) 2014 American Society of Civil Engineers.
Dams are a critical component of water infrastructure, providing services such as water supplies, recreational opportunities and flood control. At the same time, dams alter the flow regime of rivers and the biota that inhabit them. Large dams have been the subject of many studies because of their potentially significant impacts on stream hydrology and ecosystems. However, most dams are not large and consequently have received far less attention. Data for more than 5700 dams in New York State, USA located in 17 watersheds were used to develop watershed level metrics that relate the characteristics of the dams to the hydrology and demographics of each watershed. Metrics presented, stratified by watershed, include median structure age, density, dams per stream length, persons per dam, storage per drainage area, storage per person and percent high impact dams (high hazard and large). These metrics were used to perform a simple characterization of the 17 watersheds. Considerable regional differences in these parameters suggest varying management strategies in each watershed. A new era of river management has resulted in the removal of many dams, which is driven by the high cost of maintenance and state regulations. Copyright © 2013 John Wiley & Sons, Ltd.
In this article, flood protection is considered in the context of sustainability. On the one hand, floods destroy human heritage and jeopardize sustainable development, which can be defined as “non-decreasing quality of life.” On the other hand, following the most common interpretation of sustainable development, one should not choose flood protection policies that could be rated by future generations as inappropriate options of flood defense. This is how several large structural flood defenses are often viewed. Non-structural measures are in better agreement with the spirit of sustainable development, being more reversible, commonly acceptable, and environment-friendly. Among such measures are source control (watershed/landscape structure management), laws and regulations (including zoning), economic instruments, an efficient flood forecast-warning system, a system of flood risk assessment, awareness raising, flood-related data bases, etc. As flood safety cannot be reached in most vulnerable areas with the help of structural means only, further flood risk reduction via non-structural measures is usually indispensable, and a site-specific mix of structural and non-structural measures seems to be a proper solution. Since sustainability requires thinking about the future generations, the climate change issue becomes important. Non-structural measures lend themselves well to application in climate change adaptation strategies. As uncertainty in the assessment of climate change impacts is high, flexibility of adaptation strategies is particularly advantageous.
The International Commission on Irrigation and Drainage (ICID) is a scientific and technical, non-governmental international organization. The objectives of ICID are to stimulate and promote the development and application of irrigation, drainage, flood control, river training and environmental management in all their technical, economic, social and environmental aspects, as well as the needed research leading to the use of modern techniques. During the past years intensive discussions have been going on at a global scale regarding the future of dams. These discussions have mainly been initiated due to environmental concerns and resettlement problems related to the development of new reservoirs. In the light of these discussions ICID was asked to clarify its position. Since then a position paper on the 'Role of dams for irrigation, drainage and flood control' has been prepared which was almost unanimously approved by ICID's national committees. In this paper the main issues and findings as described in the position paper are presented. The future steps ICID is planning to take in order to contribute to the finding of sustainable solutions and improvements in decision-making processes on dams are also illustrated.
Studies of the effects of dams have emphasized large and very large dams; less well understood are the impacts caused by smaller dams. Using Texas as an example area, this article highlights the role of small- and medium-sized dams in affecting the surface hydrology of river systems. Analysis of data from the National Inventory of Dams (NID) in a geographic information system showed that small and medium dams comprise about 97 percent of the dams registered in Texas. A small- or medium-sized dam is found approximately every 100 km(2) of area and about 120 km of river length. Different from large dams, which affect water storage the most, the major impact of these smaller dams is fragmentation of river landscapes. Analysis of data for dams extracted from digital orthoquads and for water bodies from the National Hydrography Dataset indicates that the extent of river fragmentation is likely greater than that suggested by data from the NID, because the NID underrepresents the smaller dams. Such extent of river fragmentation can degrade stream habitats and pose barriers to the migration of aquatic species and transport of sediment. Because small and medium dams are largely built for fire protection and stock ponds, mitigating the impacts associated with these dams likely involves working with the private individuals who own them.
Floods are a natural process in which the river spills over its banks. Hazards occur when the population occupy these areas during a sequence of small floods. In South America flood impacts have occurred mainly due to the lack of flood plain management. Flood hazards in some communities on the banks of major rivers have had major social and economic impacts which can be seen many years after the event. There is an explicit conflict between dams for energy production and their use to for flood control. In the Brazilian electricity sector, these dams have been operated since the end of the 1970s, with a waiting volume that aims not only at improving their safety but also at reducing the impact of floods. In this article, the potential impacts of dams are stressed, with operational features for flood control and the description of a conflict generated between a hydropower dam and the community of two cities.
The aim of this paper is, first, to examine the record to date for river basin development in tropical Africa; and second, to examine in more detail the role and performance of institutions in this record of African river basin development. The experience of institutions with river basin development are assessed against outcomes - namely, the extent to which the resources of Africa's river basins have actually been developed in recent years and the role that institutions have played in that development.
Freshwater species and habitats are among the most threatened In the world. One way in which this growing conservation concern can be addressed is the creation of freshwater protected areas. Here, we present three strategies for fresh water protected-area design and management: whole-catchment management, natural-flow maintenance, and exclusion of non-native species, These strategies are based on the three primary threats to fresh waters: land-use disturbances, altered hydrologies, and Introduction of non-native species. Each strategy draws from research in limnology and river and wetland ecology. Ideally, freshwater protected areas should be located in intact catchments, should have natural hydrological regimes, and should contain no non-native species. Because optimal conservation conditions are often difficult to attain, we also suggest alternative management strategies, including multiple-use modules, use of the river continuum concept, vegetated buffer strips partial water discharges, and eradication of exotic species. Under some circumstances it may be possible to focus freshwater conservation efforts on two key zones: adjacent terrestrial areas and headwaters.
Land-cover change (urbanisation, deforestation, and cultivation) results in increased flood frequency and severity. Mechanisms include reduced infiltration capacity, lower soil porosity, loss of vegetation, and forest clearing, meaning lower evapotranspiration. Major research challenges lie in quantification of effects in terms of flood characteristics under various conditions, ascertaining the combined effects of gradual changes over long time periods, and developing model tools suitable for land-use management. Large floods during the 1990s gave a new focus on these problems. Reference is made to the Norwegian HYDRA research programme on human impacts on floods and flood damage.
The paper concludes that land-use change effects on floods are most pronounced at small scale and for frequent flood magnitudes. Model simulations of effects of land-use change can now be used to reduce flood risk. Modern flood management strategies have abandoned the position that dams and dikes are the only answers to mitigating flood disasters. Today, the strategic approach is more often: do not keep the water away from the people, keep people away from the water. Flood management strategies should include flood warnings, efficient communication, risk awareness, civil protection and flood preparedness routines, effective land-use policies, flood risk mapping, … as well as structural measures.
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DIN 19700-11 (July 2004). Stauanlagen -Teil 11: Talsperren. Beuth Verlag. Berlin
[8] DIN 19700-12 (July 2004). Stauanlagen -Teil 12: Hochwasserrückhaltebecken;
Maintaining small dams
- D L Pfost
- H A Curry
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The Small Dams Safety Index (SDSI): a tool for small dams safety assessment
- W Pinto
- H Fais
Pinto, W L H., & Fais, L M C F. (2022, April 4). The Small Dams Safety Index (SDSI): a
tool for small dams safety assessment. Taylor & Francis, 21(3), 551-558.
https://doi.org/10.1080/15715124.2022.2047711
Check dams worldwide: Objectives, functions, effectiveness and undesired effects
- M E Lucas-Borja
- G Piton
- Y Yu
- C Castillo
- J P Nunes
Lucas-Borja, M E., Piton, G., Yu, Y., Castillo, C., & Nunes, J P. (2021, September 1). Check
dams worldwide: Objectives, functions, effectiveness and undesired effects. Elsevier
BV, 204, 105390-105390. https://doi.org/10.1016/j.catena.2021.105390
Factors Influencing Sustainability of Rural Water Supplies Management in Kenya: A Case Study of Marakwet West Sub County
- W K Kilimo
- Nambuswa
Kilimo, W K., & Nambuswa. (2018, August 26). Factors Influencing Sustainability of
Rural Water Supplies Management in Kenya: A Case Study of Marakwet West Sub
County, Elgeyo Marakwet County, Kenya., 8(8). https://doi.org/10.6007/ijarbss/v8-i8/4444
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