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1.
Abstract

A river regime describes the average seasonal behaviour of flow. This seasonal pattern reflects climatic and physiographic conditions in the basin. An inherent characteristic of a flow regime is its stability, i.e. regularity or irregularity of the seasonal pattern. A temperature rise, as predicted by climatic models, might cause changes in the patterns and stability of river flow regimes. Sensitivity of the stability of flow regimes to small fluctuations in temperature (= ± 1°C) is investigated with the help of historical temperature and flow series for Scandinavia. The concept of entropy is utilized for quantification of the stability of the flow regimes conditioned on temperature which also allows forecasting of possible changes in this stability due to changes in temperature. The study shows that the stability of flow regime types with rain or mixed rain and snowmelt sources of flow formation is already sensitive to small changes in temperature, especially concerning flow minima.  相似文献   

2.
Abstract

A river flow regime describes an average seasonal behaviour of flow and reflects the climatic and physiographic conditions in a basin. Differences in the regularity (stability) of the seasonal patterns reflect different dimensionality of the flow regimes, which can change subject to changes in climate conditions. The empirical orthogonal functions (EOF) approach can be used to describe the intrinsic dimension of river flow regimes and is also an adopted method for reducing the phase space in connection to climate change studies, especially in studies of nonlinear dynamic systems with preferred states. A large data set of monthly river flow for the Nordic countries has been investigated in the phase space reduced to the first few amplitude functions to trace a possible signature of climate change on the seasonal flow patterns. The probability density functions (PDF) of the weight coefficients and their possible change over time were used as an indicator of climate change. Two preferred states were identified connected to stable snowmelt-fed and rainfed flow regimes. The results indicate changes in the PDF patterns with time towards higher frequencies of rainfed regime types. The dynamics of seasonal patterns studied in terms of PDF renders it an adequate and convenient characterization, helping to avoid bias connected to flow regime classifications as well as uncertainties inferred by a modelling approach.  相似文献   

3.
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4.
Abstract

Equatorial rivers of East Africa exhibit unusually complex seasonal and inter-annual flow regimes, and aquatic and adjacent terrestrial organisms have adapted to cope with this flow variability. This study examined the annual flow regime over the past 40 years for three gauging stations on the Mara River in Kenya and Tanzania, which is of international importance because it is the only perennial river traversing the Mara-Serengeti ecoregion. Select environmental flow components were quantified and converted to ecologically relevant hydraulic variables. Vegetation, macroinvertebrates, and fish were collected and identified at target study sites during low and high flows. The results were compared with available knowledge of the life histories and flow sensitivities of the riverine communities to infer flow–ecology relationships. Management implications are discussed, including the need to preserve a dynamic environmental flow regime to protect ecosystems in the region. The results for the Mara may serve as a useful model for river basins of the wider equatorial East Africa region.
Editor Z.W. Kundzewicz; Guest editor M. Acreman  相似文献   

5.
Abstract

The hydrology of water-dependent ecosystems around the world has been altered as a result of flow regulation and extraction for a variety of purposes including agricultural and urban water supply. The flow regime of the Murray-Darling Basin in Australia is no exception, with attendant impacts on the health of the environment. Restoration of parts of the flow regime is a key feature of environmental flow delivery. However, environmental flow delivery in a system that is managed primarily to provide a secure and stable supply for irrigation presents challenges for managers seeking to return more natural flow variability in line with ecosystem requirements. The institutional arrangements governing releases of water from storage can influence the ability of managers to respond to natural cues, such as naturally rising flows in a river. As such, the legal and governance aspects of environmental flow delivery are likely to be important influences on the outcomes achieved.
Editor Z.W. Kundzewicz; Guest editor M. Acreman

Citation Banks, S.A. and Docker, B.B., 2014. Delivering environmental flows in the Murray-Darling Basin (Australia)—legal and governance aspects. Hydrological Sciences Journal, 59 (3–4), 688–699.  相似文献   

6.
《水文科学杂志》2012,57(15):1932-1942
ABSTRACT

The UK Hydrological Outlook (UKHO) is a seasonal forecast of future river flows and groundwater levels. The UKHO contains both presentations of outputs from models simulating future conditions and a high-level summary. The summary is produced by an expert panel of forecasters that considers the model outputs together with other recent hydrological and meteorological information. Whilst the skill and uncertainty of the individual models have been explored and published, this study sets out to establish the performance of the high-level summary, and presents such an assessment of the river flow forecasts at the 1-month timescale. Both qualitative and quantitative assessments are presented and compared with two naïve forecasting methods. The UKHO summary is found to have a similar Gerrity skill score to a “same as last month” forecast, an outcome that generates suggestions for improvements in how the different model outputs should be considered and presented in the high-level summary.  相似文献   

7.
Regimes are useful tools for characterizing the seasonal behaviour of river flow and other hydroclimatological variables over an annual cycle (hydrological year). This paper develops and tests: (i) a regime classification method to identify spatial and temporal patterns in intraannual hydroclimatological response; and (ii) a novel sensitivity index (SI) to assess river flow regimes' climatic sensitivity. The classification of regime shape (form) and magnitude considers the whole annual cycle rather than isolating a single month or season for analysis, which has been the common approach of previous studies. The classification method is particularly useful for identifying large‐scale patterns in regimes and their between‐year stability, thus providing a context for short‐term, small‐scale process‐based research. The SI provides a means of assessing the often‐complex linkages between climatic drivers and river flow, as it identifies the strength and direction of associations between classifications of climate and river flow regimes. The SI has the potential for application to other problems where relationships between nominal classifications require to be found. These techniques are evaluated by application to a test data set of river flow, air temperature and rainfall time‐series (1974–1999) for a sample of 35 UK river basins. The results support current knowledge about the hydroclimatology of the UK. Although this research does not seek to yield new, detailed physical process understanding, it provides perspective at large spatial and temporal scales upon climate and flow regime patterns and quantifies linkages. Having clearly demonstrated the regime classification and SI to be effective in an environment where the hydroclimatology is relatively well known, there appears to be much to gain from applying these techniques in parts of the world where patterns and associations between climate and hydrology are poorly understood. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

8.
Hydrological regimes strongly influence the biotic diversity of river ecosystems by structuring physical habitat within river channels and on floodplains. Modification of hydrological regimes by dam construction can have important consequences for river ecosystems. This study examines the impacts of the construction of two dams, the Gezhouba Dam and the Three Gorges Dam, on the hydrological regime of the Yangtze River in China. Analysis of hydrological change before and after dam construction is investigated by evaluating changes in the medians and ranges of variability of 33 hydrological parameters. Results show that the hydrological impact of the Gezhouba Dam is relatively small, affecting mainly the medians and variability of low flows, the rate of rise, and the number of hydrological reversals. The closure of the Three Gorges Dam has substantially altered the downstream flow regime, affecting the seasonal distribution of flows, the variability of flows, the magnitude of minimum flows, low‐flow pulses, the rate of rise, and hydrological reversals. These changes in flow regime have greatly influenced the aquatic biodiversity and fish community structure within the Yangtze River. In particular, populations of migratory fish have been negatively impacted. The results help to identify the magnitudes of hydrological alteration associated with the construction of dams on this important large river and also provide useful information to guide strategies aimed at restoration of the river's ecosystems. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

9.
ABSTRACT

In this study, the distributed catchment-scale model, DiCaSM, was applied on five catchments across the UK. Given its importance, river flow was selected to study the uncertainty in streamflow prediction using the Generalized Likelihood Uncertainty Estimation (GLUE) methodology at different timescales (daily, monthly, seasonal and annual). The uncertainty analysis showed that the observed river flows were within the predicted bounds/envelope of 5% and 95% percentiles. These predicted river flow bounds contained most of the observed river flows, as expressed by the high containment ratio, CR. In addition to CR, other uncertainty indices – bandwidth B, relative bandwidth RB, degrees of asymmetry S and T, deviation amplitude D, relative deviation amplitude RD and the R factor – also indicated that the predicted river flows have acceptable uncertainty levels. The results show lower uncertainty in predicted river flows when increasing the timescale from daily to monthly to seasonal, with the lowest uncertainty associated with annual flows.  相似文献   

10.
ABSTRACT

The temporal dynamics of groundwater–surface water interaction under the impacts of various water abstraction scenarios are presented for hydraulic fracturing in a shale gas and oil play area (23 984.9 km2), Alberta, Canada, using the MIKE-SHE and MIKE-11 models. Water-use data for hydraulic fracturing were obtained for 433 wells drilled in the study area in 2013 and 2014. Modelling results indicate that water abstraction for hydraulic fracturing has very small (<0.35%) negative impacts on mean monthly and annual river and groundwater levels and stream and groundwater flows in the study area, and small (1–4.17%) negative impacts on environmental flows near the water abstraction location during low-flow periods. The impacts on environmental flow depend on the amount of water abstraction and the daily flow over time at a specific river cross-section. The results also indicate a very small (<0.35%) positive impact on mean monthly and annual groundwater contributions to streamflow because of the large study area. The results provide useful information for planning long-term seasonal and annual water abstractions from the river and groundwater for hydraulic fracturing in a large study area.  相似文献   

11.
Abstract

The global climate change may have serious impacts on the frequency, magnitude, location and duration of hydrological extremes. Changed hydrological extremes will have important implications on the design of future hydraulic structures, flood-plain development, and water resource management. This study assesses the potential impact of a changed climate on the timing and magnitude of hydrological extremes in a densely populated and urbanized river basin in southwestern Ontario, Canada. An ensemble of future climate scenarios is developed using a weather generating algorithm, linked with GCM outputs. These climate scenarios are then transformed into basin runoff by a semi-distributed hydrological model of the study area. The results show that future maximum river flows in the study area will be less extreme and more variable in terms of magnitude, and more irregular in terms of seasonal occurrence, than they are at present. Low flows may become less extreme and variable in terms of magnitude, and more irregular in terms of seasonal occurrence. According to the evaluated scenarios, climate change may have favourable impacts on the distribution of hydrological extremes in the study area.  相似文献   

12.
Abstract

A quasi-geostrophic numerical model of flow in a rotating channel is integrated under conditions typical of laboratory experiments with an internally heated annulus system. Compared to a laboratory experiment, or a full Navier-Stokes simulation, the quasi geostrophic numerical model is a simple system. It includes nonlinear interactions, dissipation via conventional parameterizations of Ekman layers and internal diffusion, and a steady forcing term which represents heating near the centre of the channel and cooling near both sides. Explicit boundary layers, cylindrical geometry effects, horizontal variations in static stability and variations in conductivity and diffusivity with temperature are all absent, and ageostrophic advection is incompletely represented. Nevertheless, over a range of parameters, flows are produced which strongly resemble those seen in the laboratory thus suggesting that the most important physical processes are represented. The numerical model is used to map out a regime diagram which includes examples of steady flows, flows with periodic time dependence (wavenumber vacillations) and flows which are irregularly time dependent.  相似文献   

13.
Abstract

Multidisciplinary models are useful for integrating different disciplines when addressing water planning and management problems. We combine water resources management, water quality and habitat analysis tools that were developed with the decision support system AQUATOOL at the basin scale. The water management model solves the allocation problem through network flow optimization and considers the environmental flows in some river stretches. Once volumes and flows are estimated, the water quality model is applied. Furthermore, the flows are evaluated from an ecological perspective using time series of aquatic species habitat indicators. This approach was applied in the Tormes River Water System, where agricultural demands jeopardize the environmental needs of the river ecosystem. Additionally, water quality problems in the lower part of the river result from wastewater loading and agricultural pollution. Our methodological framework can be used to define water management rules that maintain water supply, aquatic ecosystem and legal standards of water quality. The integration of ecological and water management criteria in a software platform with objective criteria and heuristic optimization procedures allows realistic assessment and application of environmental flows to be made. Here, we improve the general methodological framework by assessing the hydrological alteration of selected environmental flow regime scenarios.
Editor D. Koutsoyiannis; Guest editor M. Acreman

Citation Paredes-Arquiola, J., Solera, A., Martinez-Capel, F., Momblanch, A., and Andreu, J., 2014. Integrating water management, habitat modelling and water quality at the basin scale and environmental flow assessment: case study of the Tormes River, Spain. Hydrological Sciences Journal, 59 (3–4), 878–889.  相似文献   

14.
Abstract

A technique for generating sequences of daily streamflows is presented which preserves the important characteristics of the daily flow hydrograph by the the use of a number of simple processes. The daily flow model is applied, in conjunction with a disaggregation model to preserve statistics of monthly and annual flows, to historic data for a river in the northwest of England. Several sets of synthetic data generated by the model are tested for their acceptability.  相似文献   

15.
Abstract

This paper aims at initiating a fundamental understanding of the suspended load transport of river sediment in unsteady flow. Laboratory erosion tests as well as artificial flood experiments are used to evaluate the influence of the transient regime on the transport efficiency of the flow. The erosion experiments reveal that the transport capacity is augmented when the unsteadiness of the flow increases. However, the influence of the transient regime is counteracted by the cohesive properties of the river bed. Field experiments with artificial floods released from a reservoir into a small canal confirm these findings and show a relationship between the friction velocity and the suspended load transport. An appropriate parameter β is proposed to evaluate the impact of the transient regime on the transport of suspended sediment.  相似文献   

16.
Abstract

Environmental flows have scarcely been considered in river water management in Bangladesh. This study attempts to assess the environmental flow requirements in the Halda River, Bangladesh. Thus, the objectives are to estimate the Halda River flow with different return periods/probabilities, which was done using the log-Pearson Type III distribution (LPIII), and to mitigate the environmental problems in the Halda River using the building block method. The LPIII distribution was used to estimate the expected extreme and satisfactory flows for fish habitat at Panchpukuria station and the expected extreme water levels at Panchpukuria, Narayanhat, Telpari and Enayethat stations. It was found that floods are likely to occur at least once in 2.1, 1.02, 1.75 and 1.25 years at Panchpukuria, Narayanhat, Telpari and Enayethat stations, respectively. The results of flow and water quality analyses suggest that environmental flow requirements cannot be achieved in this river throughout the year. The environmental flow requirements and conservation of fish resources can be achieved by implementing the suggestions provided in conjunction with a comprehensive awareness programme, investigations and trade-off analyses being among the suggestions.

Editor Z.W. Kundzewicz; Associate editor B. Sivakumar

Citation Akter, A. and Ali, Md. H., 2012. Environmental flow requirements assessment in the Halda River, Bangladesh. Hydrological Sciences Journal, 57 (2), 326–343.  相似文献   

17.
《水文科学杂志》2013,58(6):1105-1120
Abstract

Under the European Union Water Framework Directive, Member States must put in place a river basin planning framework to determine what measures are necessary to maintain and improve the ecological status for all surface water bodies. The governmental organisations legally responsible for implementing the Directive in the UK have recognised that an appropriate river flow regime is fundamental to maintain a healthy river and, as a result, they need to regulate abstractions and effluent discharges and ensure sufficient water is released from impoundments. This paper reports on the process of producing environmental standards that define the maximum abstraction allowable from UK rivers, to leave sufficient flow to maintain a healthy river ecosystem. As there are currently insufficient data available to determine the relationships between river flow and ecological status empirically, expert knowledge was captured through a series of workshops at which leading UK freshwater scientists defined maximum levels of river flow regime alteration that would achieve ecological objectives for different river water body types. For the least ecologically sensitive rivers, maximum abstractions in the range 15–35% of the natural flow were proposed, depending on the flow magnitude and time of year. For the most sensitive rivers, the maximum abstraction proposed was in the range 7.5–25%. The knowledge was used by the responsible UK authorities to develop environmental standards. The authorities subsequently used the environmental standards to determine regulatory standards that could be implemented within practical constraints and current licensing policies.  相似文献   

18.
Abstract

In many of the world’s river basins, the water resources are over-allocated and/or highly modified, access to good quality water is limited or competitive and aquatic ecosystems are degraded. The decline in aquatic ecosystems can impact on human well-being by reducing the ecosystem services provided by healthy rivers, wetlands and floodplains. Basin water resources management requires the determination of water allocation among competing stakeholders including the environment, social needs and economic development. Traditionally, this determination occurred on a volumetric basis to meet basin productivity goals. However, it is difficult to address environmental goals in such a framework, because environmental condition is rarely considered in productivity goals, and short-term variations in river flow may be the most important driver of aquatic ecosystem health. Manipulation of flows to achieve desired outcomes for public supply, food and energy has been implemented for many years. More recently, manipulating flows to achieve ecological outcomes has been proposed. However, the complexity of determining the required flow regimes and the interdependencies between stakeholder outcomes has restricted the implementation of environmental flows as a core component of Integrated Water Resources Management (IWRM). We demonstrate through case studies of the Rhône and Thames river basins in Europe, the Colorado River basin in North America and the Murray-Darling basin in Australia the limitations of traditional environmental flow strategies in integrated water resources management. An alternative ecosystem approach can provide a framework for implementation of environmental flows in basin water resources management, as demonstrated by management of the Pangani River basin in Africa. An ecosystem approach in IWRM leads to management for agreed triple-bottom-line outcomes, rather than productivity or ecological outcomes alone. We recommend that environmental flow management should take on the principles of an ecosystem approach and form an integral part of IWRM.

Editor D. Koutsoyiannis

Citation Overton, I.C., Smith, D.M., Dalton J., Barchiesi S., Acreman M.C., Stromberg, J.C., and Kirby, J.M., 2014. Implementing environmental flows in integrated water resources management and the ecosystem approach. Hydrological Sciences Journal, 59 (3–4), 860–877.  相似文献   

19.
ABSTRACT

Accurate assessment of stage–discharge relationships in open channel flows is important to the design and management of hydraulic structures and engineering. Flow junctions commonly occur at the confluence of natural rivers or streams. The effect of flow junctions on the stage–discharge relationship at mountain river confluences was found by measuring velocity fields and water levels in experimental models. The results show that the backwater and accumulation–separation at flow junctions affect the flow structures and patterns in the channel; also, flow confluences may induce complex flow characteristics of backwater and flow separation at river junctions, indicating potential submerged flooding disasters within the confluence zone. The impacts of flow junctions on the stage–discharge relationship are investigated for two physical confluence models built from river confluence prototype systems in southwest China. The results show that the presence of tributary river inflows tends to increase the water level of the main river. This is important for flood control, flood-risk evaluation and engineering (e.g. hydropower station construction) in mountain rivers. Finally, a comparative quantitative analysis based on flow motion equations is conducted to evaluate the stage–discharge relationship in both uniform and regular confluence systems. The results indicate that more accurate prediction can be made when taking into account the flow non-uniformity induced by flow separation, backwater and distorted bed in the junction region.  相似文献   

20.
Abstract

Using a groundwater flow model and long historical meteorological time series data, the evolution of the groundwater flow regime in a multi-layered groundwater flow basin in northern Belgium during the last one and a half centuries (since 1833) is reconstructed. Model output parameters such as piezometric levels, depth to water table, seepage fluxes in the valleys and calculated baseflow to the river system are presented and inter-annual and decadal variations are evaluated against seasonal fluctuations. The main time-varying boundary condition in the model is the aquifer recharge which was estimated using the method of Thornthwaite and Mather based on precipitation and temperature data. The model does not take into account changes in boundary conditions due to changes in land use (deforestation, drainage of cultivated land) or groundwater exploitation. Variations in model output parameters are therefore only due to climatological forcing. Only the natural non-exploited state of the aquifer is considered. Although few historical piezometric measurements are available to verify model output, the results give an indication of the natural hydrodynamic variations on a time scale of decades.

Citation Van Camp, M., Coetsiers, M., Martens, K. & Walraevens, K. (2010) Effects of multi-annual climate variability on the hydrodynamic evolution (1833 to present) in a shallow aquifer system in northern Belgium. Hydrol. Sci. J. 55(5), 763–779.  相似文献   

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