Latitudinal gradients in runoff dynamics across undisturbed Eurasian permafrost rivers under accelerating climate change

Communities that use fill-and-draw waste-water treatment lagoons or waste-stabilization ponds are required to discharge during the spring and fall of the year at a rate that does not exceed the assimilative capacity of the receiving stream. The 10-year low mean monthly discharge (MMQj_o) for October, November, April, and May for the receiving stream has been used to establish the discharge rate for the treatment systems at the appropriate time of the year. To determine the MMQ]_Q for the receiving stream the monthly mean discharge first was estimated by using a technique developed by Once the monthly mean discharge was determined the MMQ]_Q of the ungaged stream was estimated by using a graphical correlation between the monthly mean discharge and the MMQio of a<t least three gaging stations near the waste-stabilization pond. The MMQ]_Q for these gaging stations were determined by a log-Pearson Type III frequency analysis.

Changes in the hydrological cycle are increasingly influenced by climate change. Every year, droughts and floods increase and strongly threaten the landscape, buildings, human settlements and lives. Climate data from climate scenarios are used to predict extreme events in the future. Many methods can process the climate data and evaluate the hydrological characteristics, according to which it is possible to determine the changes in the hydrological regime in the landscape. The paper aims to characterize future changes in the hydrological regime for eight selected basins of Slovakia, which were divided into four groups according to location, i.e., eastern Slovakia, northern Slovakia, central Slovakia, and western Slovakia. The input data include mean daily discharges and are divided into four groups. The first group consists of observed daily discharges provided by the Slovak Hydrometeorological Institute and represents the reference period from 1981 to 2010. The second group generates mean daily discharges using the HBV type TUW rainfall-runoff model in 1981-2010. The third and fourth groups simulate mean daily discharges using the meteorological inputs from the KNMI and MPI climate scenarios, containing data from 1981 to 2100. The available data were inputs to The Indicators of Hydrologic Alteration program, and subsequent analyses are focused on mean monthly discharges, M-day minimum and maximum discharges, the occurrence of maximum and minimum discharge, and baseflow index. For assessing the future changes in hydrological regime characteristics, the reference and future period 2070-2100 were compared. The results indicated that the spring's most significant decrease in mean monthly discharges occurred in eastern Slovakia. Summer is characterized by a decrease in mean monthly discharges throughout Slovakia, especially in eastern Slovakia. In eastern Slovakia, a decrease in selected M-day minimum discharges is also expected. Minor changes are expected in the characteristics of the 90-day minimum discharge Q90d in the Top&amp;#318;a &amp;#8211; Hanu&amp;#353;ovce and Top&amp;#318;ou gauging station. The most significant changes can be expected in the Laborec - Humenn&amp;#233; gauging station, where the 90-day minimum discharge Q90d can decrease by up to 38% compared to the reference period. The results show a rise of M-day maximum discharges of up to 50% in the gauging stations in the eastern part of Slovakia. The minimum discharge is shifted from November/January to October and the maximum from March to February/March. According to the increasing base flow index, the V&amp;#225;h River basin will have the best conditions for maintaining minimum discharges in drier periods. In the other basins, the values of the baseflow index decrease. An increase in mean monthly discharges may indicate future, increasing precipitation in given basins, predominantly in liquid form, or, on the other hand, increasing temperatures that can eliminate snow cover. &amp;#160; Acknowledgement: This study was supported by PhD student project ARPMP. The study was also supported by the Slovak Research and Development Agency under Contract No. APVV-20-0374.

In this article, the analysis of homogeneity and stationarity of the mean monthly discharges of the rivers of Ukraine was carried out by means of hydro-genetic methods with the use of observation series on 305 water gauging stations from the very beginning of the observation till 2010 inclusive. An integral curve was used for the estimates of homogeneity of the observation series. Difference-integral curves were used for estimation of stationarity of the observation series and for the study of their long-term cyclical fluctuations. It turned out that most series of the mean monthly discharges were homogeneous. The observation series that have a full cycle of long-term cyclical fluctuations (dry and wet phases) are stationary, whereas other observation series are quasi-stationary. The intra-annual streamflow redistribution occurs depending on dry and wet phases of long-term cyclical fluctuations. It is shown that the terms, the duration of periods and seasons of intra-annual streamflow distribution should define cyclical fluctuations because the mean monthly discharges change in dry and wet phases. Therefore, it is necessary to carry out development of the schemes of the components of intra-annual streamflow distribution for the rivers of Ukraine because such schemes were defined on the short observation series in 50–80s of the 20th century without considering a long-term cyclical fluctuation streamflow.

Hydrological forecasts are one of the most important aspects of applied hydrology. Such forecasts become increasingly necessary as the economy expands and utilisation of water resources in each country increases. Yet many of the requirements relating to hydrological forecasts cannot be fully satisfied at the present stage of the development of hydrology and meteorology. Hydrological forecasts are necessary in connection with the rational regulation of run-off, the utilisation of river energy, inland navigation, irrigation, water sports and water supplies. These forecasts are also of great importance in coping with dangerous phenomena and construction of hydraulic structures on rivers. The economic value of hydrological forecasts depends on their accuracy and the period of time they cover. The greater their accuracy and the longer the period they cover, the greater is their economic value in connection with planning electric power production, the operation of inland navigation, irrigation, water sports, etc. The aim of this study is to forecast the mean monthly discharges of the Karasu River in the eastern part of Turkey in the 2000 water year using the Thomas-Fiering model, which is a first order Markov model whose parameters change during the year. The stream gauging station whose mean monthly flow discharge will be estimated is Karasu River-Asagikagdiric (2154). All available data for monthly mean flow discharge are used to produce the synthetic data to enable the estimation to be made.

The El Niño Southern Oscillation (ENSO) is a major driver of climatic anomalies around the globe. How these climatic anomalies translate into hydrological anomalies is important for water resources management, but difficult to predict due to the non-linear relationship between precipitation and river discharge, and contrasts in hydrological response in regions with different hydrological regimes. In this study we investigate how ENSO-induced climatic anomalies translate into hydrological anomalies by focussing on Central Chile (29–42° S), a relatively small area affected by ENSO, that displays steep latitudinal and elevational climatic gradients. We analyse daily discharge timeseries from 178 discharge stations together with monthly temperature and precipitation data. Based on the Multivariate ENSO Index (MEI) we classified the discharge data for the time period 1961–2009 into El Niño (MEI>0.5), La Niña (MEI<-0.5) and non-ENSO periods (˗0.5>MEI<0.5), and calculated relative differences in mean monthly temperature, precipitation, and discharge, as compared to non-ENSO conditions. The results reveal that precipitation and specific discharge generally increase during El Niño events, while they decrease during La Niña events. However, there exist large spatial and seasonal variations. The mean monthly precipitation and specific discharge anomalies during both the El Niño and the La Niña phases are strongest in the semi-arid region (29-32° S), followed by the mediterranean (32°–36° S) and humid-temperate (36°–42° S) regions. During El Niño events, the semi-arid and mediterranean regions experience mean monthly specific discharge increases of up to +396.5 % and +104.5 %, respectively, and a considerable increase in the frequency and magnitude of high flows. In contrast, discharge in the humid-temperate region is most sensitive to rainfall deficits during La Niña events, as revealed by an increased frequency of low flows. We find that the different hydrological regimes (rainfall- or snow-dominated) show large contrasts in how ENSO-induced climatic anomalies are translated into hydrological anomalies, in that snowmelt induces a delayed discharge peak during El Niño, provides a minimum streamflow during dry La Niña conditions, and reduces the discharge variability in rivers. Finally, we discuss the implications for water resources management, highlighting the need for different ENSO prediction and mitigation strategies in central Chile, according to catchment hydrological regime.

<strong class="journal-contentHeaderColor">Abstract.</strong> The El Ni&ntilde;o Southern Oscillation (ENSO) is a major driver of climatic anomalies around the globe. How these climatic anomalies translate into hydrological anomalies is important for water resources management, but difficult to predict due to the non-linear relationship between precipitation and river discharge, and contrasts in hydrological response in regions with different hydrological regimes. In this study we investigate how ENSO-induced climatic anomalies translate into hydrological anomalies by focussing on Central Chile (29&ndash;42&deg; S), a relatively small area affected by ENSO, that displays steep latitudinal and elevational climatic gradients. We analyse daily discharge timeseries from 178 discharge stations together with monthly temperature and precipitation data. Based on the Multivariate ENSO Index (MEI) we classified the discharge data for the time period 1961&ndash;2009 into El Ni&ntilde;o (MEI&gt;0.5), La Ni&ntilde;a (MEI&lt;-0.5) and non-ENSO periods (˗0.5&gt;MEI&lt;0.5), and calculated relative differences in mean monthly temperature, precipitation, and discharge, as compared to non-ENSO conditions. The results reveal that precipitation and specific discharge generally increase during El Ni&ntilde;o events, while they decrease during La Ni&ntilde;a events. However, there exist large spatial and seasonal variations. The mean monthly precipitation and specific discharge anomalies during both the El Ni&ntilde;o and the La Ni&ntilde;a phases are strongest in the semi-arid region (29-32&deg; S), followed by the mediterranean (32&deg;&ndash;36&deg; S) and humid-temperate (36&deg;&ndash;42&deg; S) regions. During El Ni&ntilde;o events, the semi-arid and mediterranean regions experience mean monthly specific discharge increases of up to +396.5 % and +104.5 %, respectively, and a considerable increase in the frequency and magnitude of high flows. In contrast, discharge in the humid-temperate region is most sensitive to rainfall deficits during La Ni&ntilde;a events, as revealed by an increased frequency of low flows. We find that the different hydrological regimes (rainfall- or snow-dominated) show large contrasts in how ENSO-induced climatic anomalies are translated into hydrological anomalies, in that snowmelt induces a delayed discharge peak during El Ni&ntilde;o, provides a minimum streamflow during dry La Ni&ntilde;a conditions, and reduces the discharge variability in rivers. Finally, we discuss the implications for water resources management, highlighting the need for different ENSO prediction and mitigation strategies in central Chile, according to catchment hydrological regime.

The El Niño Southern Oscillation (ENSO) is a major driver of climatic anomalies around the globe. How these climatic anomalies translate into hydrological anomalies is important for water resources management, but difficult to predict due to the non-linear relationship between precipitation and river discharge, and contrasts in hydrological response in regions with different hydrological regimes. In this study we investigate how ENSO-induced climatic anomalies translate into hydrological anomalies by focussing on Central Chile (29–42° S), a relatively small area affected by ENSO, that displays steep latitudinal and elevational climatic gradients. We analyse daily discharge timeseries from 178 discharge stations together with monthly temperature and precipitation data. Based on the Multivariate ENSO Index (MEI) we classified the discharge data for the time period 1961–2009 into El Niño (MEI>0.5), La Niña (MEI<-0.5) and non-ENSO periods (˗0.5>MEI<0.5), and calculated relative differences in mean monthly temperature, precipitation, and discharge, as compared to non-ENSO conditions. The results reveal that precipitation and specific discharge generally increase during El Niño events, while they decrease during La Niña events. However, there exist large spatial and seasonal variations. The mean monthly precipitation and specific discharge anomalies during both the El Niño and the La Niña phases are strongest in the semi-arid region (29-32° S), followed by the mediterranean (32°–36° S) and humid-temperate (36°–42° S) regions. During El Niño events, the semi-arid and mediterranean regions experience mean monthly specific discharge increases of up to +396.5 % and +104.5 %, respectively, and a considerable increase in the frequency and magnitude of high flows. In contrast, discharge in the humid-temperate region is most sensitive to rainfall deficits during La Niña events, as revealed by an increased frequency of low flows. We find that the different hydrological regimes (rainfall- or snow-dominated) show large contrasts in how ENSO-induced climatic anomalies are translated into hydrological anomalies, in that snowmelt induces a delayed discharge peak during El Niño, provides a minimum streamflow during dry La Niña conditions, and reduces the discharge variability in rivers. Finally, we discuss the implications for water resources management, highlighting the need for different ENSO prediction and mitigation strategies in central Chile, according to catchment hydrological regime.

<strong class="journal-contentHeaderColor">Abstract.</strong> The El Ni&ntilde;o Southern Oscillation (ENSO) is a major driver of climatic anomalies around the globe. How these climatic anomalies translate into hydrological anomalies is important for water resources management, but difficult to predict due to the non-linear relationship between precipitation and river discharge, and contrasts in hydrological response in regions with different hydrological regimes. In this study we investigate how ENSO-induced climatic anomalies translate into hydrological anomalies by focussing on Central Chile (29&ndash;42&deg; S), a relatively small area affected by ENSO, that displays steep latitudinal and elevational climatic gradients. We analyse daily discharge timeseries from 178 discharge stations together with monthly temperature and precipitation data. Based on the Multivariate ENSO Index (MEI) we classified the discharge data for the time period 1961&ndash;2009 into El Ni&ntilde;o (MEI&gt;0.5), La Ni&ntilde;a (MEI&lt;-0.5) and non-ENSO periods (˗0.5&gt;MEI&lt;0.5), and calculated relative differences in mean monthly temperature, precipitation, and discharge, as compared to non-ENSO conditions. The results reveal that precipitation and specific discharge generally increase during El Ni&ntilde;o events, while they decrease during La Ni&ntilde;a events. However, there exist large spatial and seasonal variations. The mean monthly precipitation and specific discharge anomalies during both the El Ni&ntilde;o and the La Ni&ntilde;a phases are strongest in the semi-arid region (29-32&deg; S), followed by the mediterranean (32&deg;&ndash;36&deg; S) and humid-temperate (36&deg;&ndash;42&deg; S) regions. During El Ni&ntilde;o events, the semi-arid and mediterranean regions experience mean monthly specific discharge increases of up to +396.5 % and +104.5 %, respectively, and a considerable increase in the frequency and magnitude of high flows. In contrast, discharge in the humid-temperate region is most sensitive to rainfall deficits during La Ni&ntilde;a events, as revealed by an increased frequency of low flows. We find that the different hydrological regimes (rainfall- or snow-dominated) show large contrasts in how ENSO-induced climatic anomalies are translated into hydrological anomalies, in that snowmelt induces a delayed discharge peak during El Ni&ntilde;o, provides a minimum streamflow during dry La Ni&ntilde;a conditions, and reduces the discharge variability in rivers. Finally, we discuss the implications for water resources management, highlighting the need for different ENSO prediction and mitigation strategies in central Chile, according to catchment hydrological regime.

This paper presents an approach to perform statistical frequency analysis of water deficit duration and severity using respectively the geometric and exponential distributions. Monthly mean water discharges are compared to a given threshold and classified in two mutually exclusive ways. This leads to a two state random variable such that: a success represents the absence of a water deficit event (mean monthly discharge exceeds threshold), and a failure, a water deficit event (mean monthly discharge is below threshold). If we suppose that this random variable gives rise to a Markov process of order 1, then the duration of a water deficit event X (consecutive months in deficit) will have a geometric distribution. In turn, the summation of discharges in deficit will give the severity of a water deficit event which can be represented by a one-parameter exponential distribution. The threshold or base level is taken as a percentile of the observed mean discharges of a given month. This base level, which varies from month to month, can be viewed as the limit of an acceptable deficit (or energetic failure) associated to a given empirical probability of being in deficit. The second step of the approach is to estimate the value of the parameter for each distribution using the maximum likelihood method. Expressions for the estimator of a given percentile, $$\hat x_q $$ , as well as its variance are deduced. Finally, the presented models are applied to observed data.

This paper presents characteristics of the discharge regime, long-term trends and variability in Finland. A selection of long-term discharge records including both unregulated and regulated rivers and lake outlets were analysed up to the year 2004. In addition to individual time series, monthly and annual discharges from the territory of Finland were calculated for the period 1912–2004. The observed drought and flood periods are also discussed, as well as the connection between discharge regime and climate. Moreover, the periodicity of the time series is examined for a couple of sites. The Mann–Kendall trend test was applied to assess changes in annual, monthly and seasonal mean discharges, maximum and minimum flows and, in addition, the date of the annual peak flow. The trend analysis revealed no changes in mean annual flow in general, but the seasonal distribution of streamflow has changed. Winter and spring mean monthly discharges have increased at most of the observation sites. The spring peak has moved to an earlier date at over one-third of the sites. However, the magnitudes of spring high flow have not changed. Autumn flow did not show trends in general. Minimum flows have increased at about half of the unregulated sites.

Seasonal and interannual variations of flow discharge from Pearl River into sea

Trends in streamflow in the Yukon River Basin from 1944 to 2005 and the influence of the Pacific Decadal Oscillation

In many river basins in China, flood and drought coexist. Therefore, there is a strong demand to rationally utilize the flood waters. Water resources compensation characteristics analysis is the foundation of utilization of flood. In this paper, set pair analysis, a new uncertainty analysis method, was used to analyze the dry and wet compensation characteristics of the water resources parameters in the Dongjiang River, including precipitation, monthly mean discharge of Heyuan, Lin gxia, Boluo gauges. The results showed that the dry and wet encountering chance of precipitation and monthly mean discharge were rather large, there was no compensation characteristics. The monthly mean discharge in some curtain had the synchronization characteristics with the precipitation in the area. At the same time, there exists some degree of difference and opposition characteristics, indicating that there were some conditions for flood utilization in the Dongjiang River basin. Furthermore, correlation coefficient, fuzzy membership and grey correlation degree were adopted to test the result of set pair analysis. The results showed that set pair analysis provided consistent information with the traditional analysis method. The study demonstrated that the set pair analysis was an efficient method in study of water resources compensation characteristics.

This paper discusses a study of the application of global spatio- temporal climate datasets and the hydrological model STREAM (Spatial Tools for River Basin Environmental Analysis and Management Options). In the study, set up and calibration of STREAM for the reconstruction of monthly discharge for several locations in the western part of Java, Indonesia, for the period 1983- 2002 are carried out. The set up includes the preparation of monthly precipitation and temperature datasets, a digital elevation model of the domain being studied, and maps of land cover and soil water holding capacity. Discharge observations from six stations located mostly in the upper parts of major watersheds in the domain are used to calibrate the model by comparing simulated and observed discharge variables. The model performs reasonably well. Comparison between computed and observed mean monthly discharges yield correlation coefficients ranging from 0.72 to 0.93. The computed mean annual discharge in five out of six observation stations ranges between -8 and 5% with respect to the mean annual observed discharge. This study offers a tool which can be used for reconstructing historical discharge.

Changing climate and land-use practices influencing the natural stream flow processes in the Naryn river basin of Kyrgyzstan. Variations in stream flow regime over 33-years (1980 to 2012) were investigated using daily discharge data of three hydro-stations (Naryn, Ych-Terek and Uzunakmat), located in the Naryn River Basin. Mean monthly discharge (MMD), mean annual discharge (MAD), standard deviation (SD) and coefficient of variation (CV) were calculated to know the spatio-temporal variability. Similarly, Pearson’s correlation coefficient (r) was used to know the relationship between discharge and rainfall. Advanced time-series graph, exceedance probability and frequency distribution were computed using Hydrognomon (V.4.0.3) software to observe the variability and trends in discharge. The results from statistical calculations and software-based computations highlight the monthly, annual, and long term spatio-temporal discharge variability, extreme events, distribution and changes in stream flow records. This study preciously creates the frequency and trends of seasonal discharge, annual discharge cycle, and range of highest and lowest discharge flows. The weak and negative relationship (-0.2121, -0.4238) between rainfall and discharge propose for more investigation of climatic parameters and the topography of Tian Shan Mountain perhaps influencing discharge variability due to melting of glacier at high altitude. The flow regime of the Naryn river basin over the past 33-years perhaps changed due to climatic fluctuations, with the seasonal snowmelt timing (Post-Spring, Summer, Pri-Autumn), precipitations period (March-October), and large-scale land-use alterations.