Runoff changes simulated using a rainfall-runoff model

The Sacramento rainfall-runoff model has been used in experiments with 60 year daily series for the Czech part of the Labe River basin; simulations with decreased and/or increased inputs (precipitations, air temperature, evapotranspiration) provide results that could be used to appraise the runoff changes due to climatic warming.Simulations with the modified parameters are used for evaluation of runoff changes caused by landuse changes. For both purposes, the long-term data sets appear to be desirable; it is then possible to take into account accidental influences. The simulations also provide, as an output, the water contents in different zones of soil moisture; the relationships among evapotranspiration, soil moisture, and baseflow clearly appear in these results.     

Determination of optimal unit hydrographs by linear programming

A unit hydrograph (UH) obtained from past storms can be used to predict a direct runoff hydrograph (DRH) based on the effective rainfall hyetograph (ERH) of a new storm. The objective functions in commonly used linear programming (LP) formulations for obtaining an optimal UH are (1) minimizing the sum of absolute deviations (MSAD) and (2) minimizing the largest absolute deviation (MLAD). This paper proposes two alternative LP formulations for obtaining an optimal UH, namely, (1) minimizing the weighted sum of absolute deviations (MWSAD) and (2) minimizing the range of deviations (MRNG). In this paper the predicted DRHs as well as the regenerated DRHs by using the UHs obtained from different LP formulations were compared using a statistical cross-validation technique. The golden section search method was used to determine the optimal weights for the model of MWSAD. The numerical results show that the UH by MRNG is better than that by MLAD in regenerating and predicting DRHs. It is also found that the model MWSAD with a properly selected weighing function would produce a UH that is better in predicting the DRHs than the commonly used MSAD.Notations M number of effective rainfall increments - N number of direct runoff hydrograph ordinates - R number of storms - MSAD minimize sum of absolute deviation - MWSAD minimize weighted sum of absolute deviation - MLAD minimize the largest absolute deviation - MRNG minimize the range of deviation - RMSE root mean square error - P _m effective rainfall in time interval [(m–1)t,mt] - Q _n direct runoff at discrete timent - U _k unit hydrograph ordinate at discrete timekt - W _n weight assigned to error associated with estimatingQ _n - _n ⁺ error associated with over-estimation ofQ _n - _n ^– error associated with under-estimation ofQ _n - _max ⁺ maximum positive error in fitting direct runoff hydrograph - _max ^– maximum negative error in fitting direct runoff hydrograph - _max largest absolute error in fitting obtained direct runoff - E _r,1 thelth error criterion measuring the fit between the observed DRHs and the predicted (or reproduced) DRHs for therth storm - E ₁ averaged value of error criterion overR storms     

Impact of Climate Change on the Hydrological Regime and Water Resources in the Basin of Siatista

This paper examines an assessment of the impact of climate change on hydrological regimes and water resources in the basin of Siatista, a sub-basin of the Aliakmon river basin, located in Northern Greece. Initially all acquired hydrometeorological data of the study area, as well as the hydrometric data at the outlet of the basin, were analyzed and processed. A monthly conceptual water balance model was then calibrated using historical hydrometeorological data for determining changes in streamflow runoff under two different equilibrium scenarios (UKHI, CCC) referring to the years 2020, 2050 and 2100. It was found that by applying the two scenarios there will be a reduction of the mean winter runoff values, a serious reduction of summer runoff, an increase of maximum annual runoff and a decrease of minimum annual runoff values, an increase of potential and actual evapotranspiration, leading to a decrease of soil moisture, a reduction of snow accumulation and melting due to temperature increases, resulting in a decrease of spring runoff values and a shifting of the wet period towards December, resulting in severe prolongation of the dry period.     

Climatic Change Impact on Water Resources in a Systems Perspective

Global climate change related to natural and anthropogenic processes has been the topic of concern and interest world wide. Despite ongoing research efforts, the climate predictions cannot be rated any better than speculative or possible scenarios whose probability of occurrence is, at the present stage, impossible to assess. One of the most significant impacts of the greenhouse effect is anticipated to be on water resources, including different elements of the hydrologic cycle, water supply and demand, regional vulnerability, and water quality. Thus, the impact of climate change appears to be an additional component on top of the large number of existing water-related problems.The existence of the greenhouse effect, the increase of greenhouse gas emissions, and the rise of corresponding concentrations are things that are certain. However, their impacts on hydrology and water management are highly uncertain. In the latter area, one needs information on much smaller spatial and temporal scales than those used in climate studies. The objective of the present paper is to analyze the climate change impact on water resources in a system's perspective, to discuss scientific gaps, and challenge scientific issues. The role of different scales and uncertainties, as well as the hydrological view of global circulation models are also discussed. Our preparedness for probable global (climate) change is reviewed in terms of assessment, planning, design and adaptation.     

An Aquifer Management Case Study – The Chalk of the English South Downs

The Chalk aquifer of the English South Downs is very heavily utilised. The groundwater resources have enjoyed a formal programme of management which started in the 1950s, although a number of actions had been taken earlier in order to deal with saline intrusion and potential risk to groundwater quality from urbanisation. In the late 1950s the policy of leakage/storage boreholes was first adopted, whereby the leakage boreholes along the coast were pumped in winter to intercept fresh water discharge to the sea and to maximise the recharge potential inland, and inland storage boreholes were used, as much as possible, in the summer months only. A comprehensive monitoring programme supported by aquifer modelling has enabled a gradual increase in overall abstraction to take place without increasing groundwater degradation due to saline intrusion. There have been various pollution prevention strategies over the years, and these have been effective in protecting the groundwater despite the high population density and widespread agricultural activity within the South Downs. The management of the aquifer has clearly been successful; there are many lessons from this experience that can be applied to other regions and other aquifers.     

气候变化对嘉陵江流域水资源量的影响分析

 嘉陵江是长江的最大支流,流域面积约16万km2。针对2050,2100年不同的气候变化情景,选取较为不利的参数组合,根据降水、气温、湿度、风速、日照等气候要素的变化,建立潜在蒸发量模型计算流域的潜在蒸发量（ET0）,再根据流域内植被的蒸散发系数（Kc）,计算流域的面平均蒸散发量（ETc）。并利用流域面平均降水量减去径流深得到流域的实际蒸散发量,对计算的流域面平均蒸散发量进行验证。对不同的水平年利用降水的预测成果（气候变化情景不同具有不同的降水量预测成果）及计算流域的面平均蒸散发量,根据水量平衡模型分析计算气候变化对嘉陵江流域水量的影响。结果表明：不利条件下2050年年径流将减少23.0%～27.9%;2100将减少28.2%～35.2%;2050,2100年平均年径流分别相当于目前7年一遇和12年一遇的干旱年。由此说明,气候变化对流域内的水资源量影响十分显著。      

Assessment of Snowmelt Runoff Using Remote Sensing and Effect of Climate Change on Runoff

Runoff regimes in Himalayan basins are controlled mainly by melting of snow and ice cover. The air temperature is the principal variable to estimate the importance of the melting of the snow cover when using snowmelt runoff model. Changes in temperature will ultimately affect stream flow and snow/ice melt runoff in particular. Global atmospheric general circulation models (GCMs) have been developed to simulate the present climate and used to predict future climatic changes and its effect. These GCMs have certain disadvantages, therefore another simple approach of hypothetical scenarios have been developed and successfully demonstrated in this study to investigate the effect of changes in temperature. Adopted plausible climate scenarios included three temperature scenarios (T + 1, T + 2, T + 3°C). The effect of these changes has been studied on the stream flow which has contribution from snowmelt, rainfall and base flow in the Satluj basin. It was observed that with the increase in temperature there is not much change in total stream flow, but the distribution of stream flow have changed. More snowmelt runoff occurred earlier due to increased snow melting however, reduced in the monsoon months.     

Impacts of Hydrological Changes on Annual Runoff Distribution in Seasonally Dry Basins

Runoff is expected to change due to climate and land use change. Because it constitutes a large component of the terrestrial water budget, we need to develop new policies for managing regional water resources. To do so, we must first attribute changes in the natural flow regime to either climate or land use change. In this context, the Budyko’s curve has previously been adopted to separate the impacts of climate and land use change on runoff by using long term hydrological variables. In this study, a framework based on Fu’s equation (which describes Budyko’s curve) is used to separate the impacts of climate and land use change on annual runoff distributions. Specifically, this framework is based on a recently developed method to obtain annual runoff probability density function (pdf) in seasonally dry basins—such as those in Mediterranean regions—from climate statistics and Fu’s equation parameter ω. The effect of climate change is captured through variations in the first order statistics of annual rainfall and potential evapotranspiration, while land use change is represented by changes in Fu’s equation parameter ω. The effects of these two drivers (i.e., climate and land use change) are analyzed by reconstructing the annual runoff pdfs for the current period and for likely future scenarios, based on predictions from global circulation models and urbanization trajectories. The results show that climate change can lead to a strong reduction in mean annual runoff, a shift of the runoff pdf toward lower values, and a decrease in its variance. Concurrent changes in climate and land use almost always result in a reduction in the mean annual runoff, due to the greater impact of climate change on the runoff pdf.

     

Analysis of the effect of climate change on the Nakdong river stream flow using indicators of hydrological alteration

This study models the effect of climate change on runoff in southeast Korea using the TANK conceptual rainfall-runoff model. The results are assessed using the indicators of hydrological alteration (IHA) developed by U.S. Nature Conservancy. Future climate time series are obtained by scaling historical series, provided by four global climate models (GCMs, IPCC, 2007) and three greenhouse gas (GHG) emissions scenarios (IPCC, 2000), to reflect a maximum increase of 3.6 °C in the average surface air temperature and 33% in the annual precipitation. To this end, the spatio-temporal change factor method is used, which considers changes in the future mean seasonal rainfall and potential evapotranspiration as well as the daily rainfall distribution. In this study, the variance range for precipitation is from +3.55% to +33.44% compared to the present for years between 2071 and 2100. The variance range for the daily mean temperature is estimated between +1.59 °C and +3.58 °C. Although the simulation results from different GCMs and GHG emissions scenarios indicate different responses of the flows to the climate change, the majority of modeling results show that there will be more runoff in southeast Korea in the future. According to the analysis results, the predicted impacts of hydrological alteration caused by climate change on the aquatic ecosystem are as follows: 1) an increase in the availability of aquatic ecosystem habitats in Nakdong River in future summers and winters, 2) an increase in stress on the aquatic ecosystem due to extremely high stream flow, 3) an increase in the stress duration of flood events for the Nakdong River downstream and 4) an increase in aquatic ecosystem stress caused by rapid increases or decreases in stream flow.     

Optimization of the water chemistry of the primary coolant at nuclear power plants with VVÉR

Results of the use of automatic hydrogen-content meter for controlling the parameter of hydrogen in the primary coolant circuit of the Kola nuclear power plant are presented. It is shown that the correlation between the hydrogen parameter in the coolant and the hydrazine parameter in the makeup water can be used for controlling the water chemistry of the primary coolant system, which should make it possible to optimize the water chemistry at different power levelsTranslated from Élektricheskie Stantsii, No. 12, December 2004, pp. 31 – 33.