Managed aquifer recharge (MAR) by the construction of subsurface dams in the semi-arid regions: A case study of the Kalangi river basin, Andhra Pradesh

Overuse of groundwater in coastal areas, due to high population and agricultural activity results in seawater intrusion into the coastal aquifer. This paper presents the control measures taken to manage aquifer recharge (MAR) and also to overcome the problem of seawater intrusion into the coastal aquifer along the Kalangi river, Nellore district of Andhra Pradesh, India having connectivity with Pulicat (saltwater) lake estuary. Due to overexploitation of groundwater and less rainfall in past years, adjacent seawater has started intruding in the Kalangi river sub-surface and deteriorating groundwater quality up to 11.6 km from the confluence of the river with Pulicat lake. To prevent this situtation, subsurface dams were constructed in traditional manner using local earth material in three different places across the Kalangi river near Sullurpet town. The water storage capacities calculated after the sub-surface dams’ construction are 1.28 mcft at GK Engineering College, 6.23 mcft at Challamagudi and 3.143 mcft at Holy Cross School sites. The Holy Cross School sub-surface dam is the first full scale dam-cum-check dam constructed to prevent salt water intrusion in the Kalangi river at Sullurpet, Nellore district, Andhra Pradesh. At the Kalangi river estuary portion (at the mouth of sea) a groyne was reconstructed over old groyne site with the introduction of clay bed and wooden sheet piles at down stream. Apart from prevention of sea water entry into Kalangi river sub-surface (during seasons) the groyne top level was raised to prevent mixing of high sea water tides with fresh water and ensuring additional storage of fresh water at upstream side. The reconstructed groyne was serving the purpose of obstructing the surface seawater entry in the Kalangi river and water quality has improved in the river as well as in the wells. After construction of sub-surface dam, as per the Simpson ratio classification, there is substantial improvement of water quality in the SHAR infiltration well situated near the Holy Cross School sub-surface dam.     

Earth dam site selection using the analytic hierarchy process (AHP): a case study in the west of Iran

Earth dam site selection is one of the most important problems in water resources management. It depends on a set of qualitative and quantitative criteria, and they may even be in conflict with each other. This study aims to develop a multicriteria decision-making approach to locate the dam site and construct a multipurpose earth dam in Harsin City at the western part of Iran. For this purpose, firstly, the influential criteria for locating the earth dam site were determined using a comprehensive literature review and the experts’ opinions. Then, some watersheds in the surrounding areas of Iran’s Harsin City were studied and four feasible sites proposed. In the final stage, these sites, in order to construct a multipurpose earth dam, were prioritized using the analytic hierarchy process approach and the most optimal site was selected.     

小型水坝拆除后河貌演变模拟分析——以西河水坝为例

小型水坝随着服役时间的增长,其面临的安全、经济和生态方面问题日益突出,针对一些修复价值较低的病险水坝,实施降等或报废拆除已成为一种综合最佳的管理措施。拆坝后,原库区大量淤沙无控释放将改变原有河道形态,对水生生物栖息地造成影响。为预测拆坝后河道在不同时间尺度上的变化特征,以长江流域乌江水系内的西河水坝为研究对象,建立二维水沙数学模型,分别研究了拆坝后水沙输运造成的短期和长期河床形态变化。结果表明:拆坝后短期内,坝址上游主河道发生了强烈的冲刷下切,且水库淤沙前缘部分出现了显著的淤积抬高,相比而言,坝址下游河床变化并不明显,只有坝下河段及河口附近出现较显著的泥沙淤积;在拆坝后长期的河床演变过程中,坝址上下游河道均发生了不同程度的冲刷下切,拆坝2年后下游河床逐渐趋于稳定,而上游主河道由冲刷下切转化为冲淤交替的演变趋势,河床形态不断调整变化。本研究可为病险坝和小水电报废拆坝后的河道治理、水生生物栖息地修复提供参考依据。     

Performance evaluation of correction coefficients to optimize sediment rating curves on the basis of the Karkheh dam reservoir hydrography,west Iran

The prediction of useful lifetime of a dam is estimated through accurate estimate of river sediments which mostly depend on sediment rating curve. Over the past decades, various methods have been developed by investigators. With respect to the importance of this issue, in the present study, the best discharge-sediment relationship for Jelogir hydrometric station located at the upstream of Karkheh reservoir dam is presented. In the first step, sediment rating curves in annual, seasonal, monthly, wet and dry, and middle of the classes linear ways and applying 3 correction coefficients that include Smearing, FAO, and QMILE were obtained; then, their performance was evaluated. Comparison of these results with data obtained from hydrographical operation of Karkheh dam reservoir showed that the optimal equation of discharge-sediment at this hydrometric station follows annual linear sediment rating curve with QMILE correction coefficient. According to the results, annual method has estimated sediment volume less than the actual volume, about 98.7% of the actual sediment, while other evaluated methods have showed sediment volume more than the actual one, and among correction coefficients, the application of QMILE correction coefficient is more reasonable than other coefficients.     

How to update design floods after the construction of small reservoirs and check dams: A case study from the Daqinghe river basin,China

Several small reservoirs and a large number of check dams had been constructed in the Wangkuai reservoir watershed after 1970s, and flood time series lacked stationarity, which affected the original design flood hydrographs for the Wangkuai reservoir. Since the location, storage capacity and drainage area of the large number of check dams were unknown, we present a method to estimate their total storage capacities (TSC) and total drainage areas (TDA) by using the recorded rainstorm and flood data. On the basis of TSC and TDA, the flood events which occurred in an undisturbed period were reconstructed under current conditions to obtain a stationary flood series. A frequency analysis was subsequently performed to assess the design flood peak and volume for both small and medium design floods with a 10–200 year return period. For large and catastrophic floods, it was assumed that the upstream check dams and small reservoirs would be destroyed, and water stored in these hydraulic structures were re-routed to the Wangkuai reservoir by unit hydrograph. The modified flood peak and volume decreased for floods with a 10–200 year return period when compared to the current design flood. But for large design floods with a return period exceeding 500 years, peak discharge increased. This study provides a new method for design flood calculation or modification of the original design flood in watersheds with a large number of check dams.     

Method of leakage study at the karst dam site. A case study: Khersan 3 Dam,Iran

The excellent topographic condition of the limestone canyons for dam construction may be rejected if they are karstified. Karst features cause the reservoir not to be impermeable enough to permit the water to fill it and leakage occurs and often increases with time. Moreover, karst features may involve the stability of the dam itself. A few operated dam sites at the Zagros Zone encountered a leakage problem. Furthermore, more than 30 dams are presently under study for construction in the Zagros Zone. Karst conditions and leakage potential were investigated at an under-study site (Khersan 3 Dam) for assessing the general methodology for the study of leakage potentials. Conventional methods for studying karst features, geological mapping, geomorphology and extensive borings were applied before the dam was constructed. These methods are not efficient enough to precisely reveal the karst structure, especially hidden and paleokarst, nor the hydrological behaviour of the karst structure in different settings of groundwater flow. Based on the present case study and previous applied approaches by other authors, this paper introduces a methodology by means of karst structure and functioning approaches at local and regional scales that cover the conventional methods and overcome their shortages. The proposed methodology should be applied before construction of a dam and should include three steps (a) recognition of geological and hydrogeological settings, (b) delineation and functioning of the karst system related to the future reservoir, and (c) assessment of the leakage potentials. Following this methodology, the most probable leakage zone(s) and path(s) at the dam site can be highlighted.     

Scale,governance and the management of river basins: A case study from Central Iran

Aquatic socio-ecological systems show pervasive cross-scale interactions and problems of fit between ecosystems and institutions. Nested bio-hydrological processes within river basins are prone to third-party impacts, and equitable/sustainable management of water resources requires adequate governance patterns that both cover relevant scalar levels and handle cross-scale interactions. This paper provides the example of the Zayandeh Rud basin, in central Iran, and describes the historical evolution of water use at three different nested scales. It shows how the gradual overallocation of water resources (basin closure) and the manipulation of the hydrological cycle by the state and other actors have resulted in a constant spatial and social redistribution of water use and associated benefits and costs. State-centered modes of governance characterized by the priority to large-scale infrastructure, vested political and financial interests, lack of attention to local processes and hydrological interconnectedness, and the neglect of environmental degradation, must give way to forms of comanagement that better articulate the different levels of control and governance.     

Evaluating the effect of heat waves on early melting of snow covers of Karkheh catchment in Iran

Natural Hazards - The present study aims to evaluate the effect of heat waves on the early melting of snow cover in the Karkheh catchment of Iran. After collecting daily data on the maximum...     

The role of blocking system in heavy precipitation of Iran (a case study: southeast of Iran January 2008)

This article concerns the analysis of the heavy precipitation, which allows investigating the effect of the blocking system on the unusual precipitation and temperature occurrence in Iran. The days of January 2008 have been the coldest days during the history of recorded data in Iran. Variation of precipitation during January 2008 compared with long-term data (30 years) shows the maximum positive anomaly in the stations located in southeast of Iran. However, the precipitation in consecutive days, 14–15 and 15–16 of January, produce a more important proportion of the heavy precipitation in this region. In order to study the role of the blocking system related to heavy precipitation in January 2008, the position and movement of the atmospheric systems including cyclones, anticyclones, fronts, and wind fields have been analyzed by the use of synoptic maps by the environment to circulation approach. Consequently, the weather maps indicated that the blocking system over the north of the Caspian Sea has caused the relatively deep low trough on January 5, 7, 14, 15, and 16, 2008, while the thermal and moisture gradients in the warm section of air masses have produced heavy precipitation. As a result, wind field of low levels (850 hPa) provided remarkable moisture fed by the Arabian Sea, Oman Sea, and Persian Gulf in the study area. Furthermore, the speed of wavelength and the position of the blocking system associated with the heavy precipitation can be clearly identified.     

Recent evolution of the Outardes Estuary, Quebec, Canada: consequences of dam construction on the river

The Outardes Estuary (Quebec) is a regressive sandy system developed in a sub-boreal climatic setting. The Outardes River drains an area of 18 780 km² and was dammed for hydroelectric purposes in the 1960s and‘70s. By reconstructing the hydrographs and mapping the morphology of the estuary from aerial photographs over a period of 21 years, we have documented the changes in the estuary resulting from the modification of the hydrologic regime. Until the mid-1960s, a catastrophic spring freshet (1800–2800 m³3s^-1) controlled the morphology of the estuary. The mouth was dominated by a disorganized, braided channel pattern, and large fluvial discharge-generated transverse bars. Peripheral channel areas in the upper estuary were zones of transport at flood stages. For 18 months in 1968 and‘69 the river discharge was drastically reduced (50 m³s^-1) to accomplish the main reservoir filling. Tidal currents and waves filled and remodelled the morphology of the mouth of the estuary, while the peripheral zones in the upper estuary experienced low-energy sedimentation. Since the generating plants were brought on-line in 1969, the fluvial discharge has been unable to modify substantially the sand body geometry in the mouth of the estuary. In the upper estuary the peripheral regions continue to be filled in, but the thalweg is being eroded. Based on the results of our coring programme, we suggest that major environmental changes may leave a sedimentary signature (addition or subtraction of size modes) which can be identified by the detailed analysis of grain size distributions.     

Hydraulic geometry change of a large river: a case study of the upper Yellow River

Study on hydraulic geometry can reveal the response of river systems to basin attributes, and the trends in channel change. Based on 35 years of data collected at 10 hydrological stations (cross-sections), the hydraulic geometry relations between cross-sectional variables and discharge were established, and the derived parameters were analyzed. The channel behavior of the mountainous bedrock reach (from riverhead to Xunhua cross-section) and the alluvial reach (from Xunhua to Toudaoguai cross-sections) differed significantly over the past decades in response to dramatic water and sediment changes. The hydraulic geometry quasi-equilibrium was achieved through equally adjusting water depth and flow velocity in the mountainous bedrock reach; while primarily through flow velocity in the alluvial reach. The change rate of river width with varying discharge was relatively small in the whole upper Yellow River. Compared with the lower Yellow River and other rivers in the world, both similarity and differences existed, indicating the general adjustment direction of hydraulic quasi-equilibrium and also the importance of considering other influencing factors in hydraulic geometry studies. In addition, dams played an important role in affecting the changes of hydraulic geometry exponents.     

Groundwater quality degradation of urban areas (case study: Tehran city,Iran)

Groundwater quality of Tehran city is considered in this study. Nine sampling stations were selected, and composite sampling campaign was performed in summer 2012. Groundwater sampled from northern stations appeared to have acceptable characteristics for agricultural and drinking uses. The southern station samples did not meet the required guidelines. Concentration of SO₄ ^2?, Na⁺ and Cl^? obey a sharp ascending trend southwards. Accordingly, the electrical conductivity of the last station at the very southern areas is more than fifteen times greater than that of the first northern station. Tehran city is located in a semi-arid climate and experiences long hot summers. High rates of evapo-transpiration within urban green spaces and agricultural lands facilitate the salinization phenomenon in root zones. As a result, excess irrigation water eases the consequent percolation into aquifers. Furthermore, saline water intrusion from salt marshes located down south of the city is an expected consequence of wells overpumping. Such case is especially remarkable in hot seasons when an increased urban water demand is observed. Remarkable sulfate concentrations in saline water are mainly justified by percolation of sulfate containing fertilizers which are broadly used by local farmers in an uncontrolled manner. Surface run-offs and municipal wastewater leakage may also trigger the salinization process.     

Impact of climate change on landslides frequency: the Esino river basin case study (Central Italy)

Researchers have long attempted to determine the amount of rainfall needed to trigger slope failures, yet relatively little progress has been reported on the effects of climate change on landslide initiation. Indeed, some relationships between landslides and climate change have been highlighted, but sign and magnitude of this correlation remain uncertain and influenced by the spatial and temporal horizon considered. This work makes use of statistically adjusted high-resolution regional climate model simulations, to study the expected changes of landslides frequency in the eastern Esino river basin (Central Italy). Simulated rainfall was used in comparison with rainfall thresholds for landslide occurrence derived by two observation-based statistical models (1) the cumulative event rainfall–rainfall duration model, and (2) the Bayesian probabilistic model. Results show an overall increase in projected landslide occurrence over the twenty-first century. This is especially confirmed in the high-emission scenario representative concentration pathway 8.5, where according to the first model, the events above rainfall thresholds frequency shift from ~?0.025 to ~?0.05 in the mountainous sector of the study area. Moreover, Bayesian analysis revealed the possible occurrence of landslide-triggering rainfall with a magnitude never occurred over the historical period. Landslides frequency change signal presents also considerable seasonal patterns, with summer displaying the steepest positive trend coupled to the highest inter-model spread. The methodological chain here proposed aims at representing a flexible tool for future landslide-hazard assessment, applicable over different areas and time horizons (e.g., short-term climate projections or seasonal forecasts).     

筑坝对河流生态系统影响研究进展

河流是陆地生态系统和水生态系统间物质循环的通道,筑坝人为改变河流物理、化学、生物地球化学循环模式,影响河流生态系统的结构、功能.分析了筑坝对河流水文水力特性、生源要素(氮、磷、硅等)、水生态系统结构和功能的影响以及河流生态系统恢复等研究的进展.随着水库成为陆地水分循环的一个主要组成部分,对流域生态系统健康的影响日益显著,进而对大坝的生态效应、河流生态恢复等需要进行深入的研究,减轻大坝的负面效应.     

The effects of removing bed materials on flow velocity (case study: Zaremrood River, Iran)

Nowadays, in parts of Iran, rivers and flood plains are being used as sand and silt mines, and the removal of river bed materials is performed without studying its effects on hydraulic behavior. On the other hand, the flood plain lands are in danger of floods and bank erosion. Zaremrood River in Tajan watershed due to removal of river bed material, two planes of before and after removal with scale of 1:1,000, has been used as basic data. The field investigation was emphasized on the end part of Zaremrood with a length of 5 km and starts from Ghandikola village to Ahoodasht Bridge. Using total station and field observations, the characteristics of reaches and cross sections of right bank, left bank, and main bed of river are written separately. Using software of HEC-RAS, ArcView 3.2, and extension HEC-GeoRAS, the flood zoning with different return periods to investigate water velocity and its changes, geometrical simulation of the bed, sides and flood way of rivers, and then by entering the results of HEC-GeoRAS into hydraulic software HEC-RAS for two before and after planes have been performed, and flow velocity was analyzed for three return periods of 10, 50, and 100 years. The results of this research showed that the velocities due to removal for floods with different return periods have increased, whereas water height and level during removal period have decreased.     

A proposed geotechnical-based method for evaluation of liquefaction potential analysis subjected to earthquake provocations (case study: Korzan earth dam, Hamedan province, Iran)

During the earthquakes, a number of earth dams have had severe damages or suffered major displacements as a result of liquefaction, thus modeling by computer codes can provide a reliable tool to predict the response of the dam foundation against earthquakes. These modeling can be used in the design of new dams or safety assessments of existing ones. In this paper, on the basis of the field and laboratory tests and by combination of several software packages a seismic geotechnical-based analysis procedure is proposed and verified by comparison with computer model tests and field and laboratory experiences. Verification or validation of the analyses relies to the ability of the applied computer codes. By using the Silakhor earthquake (2006, M _s 6.1) as a basis in order to check the efficiency of the proposed framework, the procedure is applied to the Korzan earth dam of Iran which is located in Hamedan Province to analyze and estimate the liquefaction and safety factor. Design and development of a computer code by the authors which was named as the ??Abbas Converter?? with graphical user interface which operates as logic connecter function that can compute and model the soil profiles is the critical point of this study. The results confirmed and proved the ability of the generated computer code on the evaluation of soil behavior during earthquake excitations. Also, this code was able to facilitate this study better than previous ones have, taking over the encountered problem.     

Hydrological responses to rainfall variability and dam construction: a case study of the upper Senegal River basin

The understanding of the spatial and temporal dynamic of river systems is essential for developing sustainable water resource management plan. For the Senegal River, this subject is very complex according to the context of (1) transboundary basin, (2) several contrasted climatic zones (Guinea, South Sudanian, North Sudanian and Sahelian) with high rainfall variability and (3) high human pressures (dam construction and water uses). From 1954 to 2000, 80% (mean value) of the Senegal River flows recorded downstream part of the basin are provided by three majors tributaries (Bafing, Bakoye and Faléme) located in the upstream part. Then, in our study, this upper Senegal River basin was chosen in order to investigate the hydrological responses to rainfall variability and dam construction. Two nonparametric statistical methods, Mann–Kendall and Hubert test, were used to detect the long-term changes in the time series of precipitation and water discharge (1954–2000) at the annual and seasonal scales. The continuous wavelet transform (Morlet Wavelet) was employed to characterize the different mode in the water discharge variability. Flow duration curve and cumulative curve methods were used to assess the impact of dams on the hydrological regime of the Senegal River. Results showed that the Senegal River flows have been changing under the influence of both rainfall variation and dam construction. The long-term evolution of water discharge depend on long-term rainfall variability: The wet periods of the 1950s and 1960s correspond to periods of higher river flows, while the droughts of the 1970s and 1980s led to unprecedented river flows deficits. The new period, since 1994, show a high inter-annual variability of rainfall and discharge without clear trend. At seasonal scale, the results showed also a strong relationship between rainfall and runoff (R ² > 0.8) resulting from alternating wet and dry seasons and rapid hydrological responses according to annual rainfall. Nevertheless, the observed flows during dry seasons highlighted the influence of water storage and restitution of infiltrated waters in soils and surficial formations during wet seasons. In the dry seasons, the water budget of the three upstream tributaries showed a water deficit at the downstream gauging station. This deficit was characterized by water loss to underlying aquifers and highlighted the influence of geological setting on water balance. However, in this context, water restitution during the dry season remained dependent on climatic zone and on the total annual rainfall volume during the previous wet season. The results have highlighted an impact of the Manantali dam previously obscured: The dam has no effect on the regulation of high river flows. That is what explains that since its construction in 1988, flooding of coastal cities, like Saint-louis, by seasonal river floods has not ceased. The flooding risk in coastal cities is not avoided, and the dams caused hyper-salinization of the Senegal lower estuary. The breach created in the coastal barrier of the Langue of Barbary in October 2003 promotes direct export of excess floodwater to the sea and reduces this risk of flooding in the delta area. But, this solution led to considerable loss of potential water resources, and the authors recommend a new water management plan with a global focus. However, this study shows the positives impacts of the two dams. They allow the availability of freshwater in order to support agricultural irrigation in the valley and delta zone, in particular during low flows periods.     

Dendrogeomorphological analysis of landslides on the undercut river terrace bank (a case study in Czech Republic)

Landslides - The steep scarps of river terraces surrounding the floodplains of meandering rivers are locations with concentrations of active geomorphic slope processes. Thus, knowledge of their...     

Correction to: Impact of climate change on landslides frequency: the Esino river basin case study (Central Italy)

We refine the 1-D velocity model of the Central India Tectonic Zone (CITZ) using well-selected arrival times of P- and S-phases of 354 local earthquakes of magnitude (M_w) between 2.0 and 5.8, recorded by national seismic network from May 1997 to March 2016. Further, we have determined the source mechanisms of 26 selected local events using moment tensor inversion to characterize the dynamics beneath the CITZ. The best-fit simulation between observed and synthetic waveforms obtained the nodal and auxiliary planes of the each faults associated with the earthquake moment magnitude (M_w) for each event. Depth of the fault plane along the CITZ varies from 5 to 38 km. From this study, we found that the western part along the CITZ shows minimum focal depth and reaches maximum 38 kms at Jabalpur in the eastern part. This complex nature of earthquake dynamics occurrence along the CITZ. We propose that the curviplanar the CITZ dominated with sinistral curvature is subjected to compression along the longer ~E–W segments and transtension along shorter segments with ~NE–SW orientations. The occurrences of normal faulting, intrusion of mafic plutons and CLVD mechanisms for earthquakes are interpreted to be linked to the transtension zones and reverse mechanisms associated with the compressions along ~E–W segments.