Assessment of streamflows in the Hornád river basin and analysis of trends

Climate change is a global phenomenon. The more frequent occurrence of dry periods, which last longer but also extreme rainfall, needs to be reduced for better water management. During the dry season, the quantity and quality of surface and groundwater decreases. Water is important for agriculture, agriculture and ecosystems. This study was focused on the occurrence of trends in daily flows in the Hornád basin at selected hydrological stations for the period 1960-2011. The Mann-Kendall trend test is used to evaluate trends in hydrometeorological time series.

Stratégies d'adaptation des producteurs agricoles aux risques hydroclimatiques dans le bassin Béninois de la pendjari à l'exutoire de Porga

West Africa's dependence on the increased impacts of extreme hydroclimatic hazards increases the vulnerability of food production to the resulting risks. This study analyses the adaptation strategies developed by agricultural producers in the Beninese Pendjari basin to cope with hydroclimatic risks. The methodological approach adopted consisted in the use of climatological data (height of daily and monthly rainfall) from the Tanguiéta and Natitingou stations over the period from 1965 to 2017 obtained in Météo-Bénin . Hydrological data consisting of the daily flows of the river calculation of the Pendjari indices at the Porga outlet, over the period 1965–2017 are extracted from the database of DG-Water and ltulization of socio-anthropological data. To better appreciate the adaptation strategies developed, a semi-structured survey that involved 121 people in 21 villages of the Beninese Pendjari basin is conducted according to the CAP approach (Knowledge, Attitudes, Practices). Direct observations in the field have also made it possible to better identify peasant adaptation strategies to the effects of hydroclimatic risks in the Beninese Pendjari basin. The information collected during the surveys was processed with Sphinx software. We studied socio-anthropological data, and we showed that Pendjari watershed in Benin is under the threat of hydroclimatic risks. To reduce their vulnerability, producers in the Benin Pendjari basin are developing several risk prevention and disaster management strategies. These include transplanting crops including sorghum by 100 % of the producers met, the disposal of logs, the enhancement of the shallows. In view of the effectiveness of the strategies identified and the limitations they present, it is important that the authorities develop a policy that is more sensitive to hydroclimatic risks, in order to improve the adaptation capacity of agricultural producers.

Water resources summary for the Snake River and Jackson Lake Reservoir in Grand Teton National Park and John D. Rockefeller, Jr. Memorial Parkway: Preliminary analysis of 2016 data

This report summarizes discharge and water quality monitoring data for the Snake River and Jackson Lake reservoir levels in Grand Teton National Park and John D. Rockefeller, Jr. Memorial Parkway for calendar year 2016. Annual and long-term discharge summaries and an evaluation of chemical conditions relative to state and federal water quality standards are presented. These results are considered provisional, and may be subject to change. River Discharge: Hydrographs for the Snake River at Flagg Ranch, WY, and Moose, WY, exhibit a general pattern of high early summer flows and lower baseflows occurring in late summer and fall. During much of 2016, flows at the Flagg Ranch monitoring location were similar to the 25th percentile of daily flows at that site. Peak flows at Flagg Ranch were similar to average peak flow from 1983 to 2015 but occurred eleven days earlier in the year compared to the long-term average. Peak flows and daily flows at the Moose monitoring station were below the long-term average. Peak flows occurred four days later than the long-term average. During summer months, the unnatural hydro-graph at the Moose monitoring location exhibited signs of flow regulation associated with the management of Jackson Lake. Water Quality Monitoring in the Snake River: Water quality in the Snake River exhibited seasonal variability over the sampling period. Specifically, total iron peaked during high flows. In contrast, chloride, sulfate, sodium, magnesium, and calcium levels were at their annual minimum during high flows. Jackson Lake Reservoir: Reservoir storage dynamics in Jackson Lake exhibit a pattern of spring filling associated with early snowmelt runoff reaching maximum storage in mid-summer (on or near July 1). During 2016, filling water levels and reservoir storage began to increase in Jackson Lake nearly two weeks earlier than the long-term average and coincident with increases in runoff-driven flows in the Snake River. Although peak storage in Jackson Lake was larger and occurred earlier than the long-term average, minimum storage levels were similar to the long-term average.

Estimation of Hourly Flood Hydrograph from Daily Flows Using Artificial Neural Network and Flow Disaggregation Technique

Flood data on a high temporal scale are required for the design of hydraulic structures, flood risk assessment, flood protection, and reservoir operations. Such flood data are typically generated using rainfall-runoff models through an accurate calibration process. The data also can be estimated using a simple relationship between the daily and the sub-daily flow records as an alternative to rainfall–runoff modelling. In this study, we propose an approach combining an artificial neural network (ANN) model for peak flow estimation and the steepness index unit volume flood hydrograph (SIUVFH) method for sub-daily flow disaggregation to generate hydrographs on an hourly time scale. The SIUVFH method is based on the strong relationship between the flood peak and the steepness index, which is defined as the difference between the daily flood peak and daily flow several days before the peak; it is also used for selecting a reference unit volume flood hydrograph to be scaled to obtain the sub-daily flood hydrograph. In this study, to improve the applicability of the SIUVFH method for locations with a weak relationship between the flood peak and steepness index, the ANN-based flood peak estimation was used as an additional indicator to determine a reference unit volume flood hydrograph. To apply the proposed method, ANN models for estimating the peak flows from the mean daily flows during peak and adjacent days were constructed for the studied dam sites. The optimal ANN structures were determined through Monte Carlo cross-validation. The results showed a good performance with statistical measurements of relative root mean square errors of 0.155–0.224, 0.208–0.301, and 0.244–0.382 for the training, validation, and testing datasets, respectively. An application of the combined use of the ANN-based peak estimation and the SIUVFH-based flow disaggregation revealed that the disaggregated hourly flows satisfactorily matched the observed flood hydrograph.

A regional flow type classification for South African perennial rivers

Flow classification provides a statistically robust method of defining an expected range of variability for flow metrics describing frequency, magnitude, duration and timing of events. Here, we characterised reference mean daily flows for 1950–1999 for all 5 838 quinary catchments of South Africa based on 150 metrics. Using a two-tiered approach, where sub-catchments were classified into similar flow types using principal components and cluster analyses, we defined 6 to 12 flow types for each of 8 hydrological regions reflecting rainfall seasonality. Redundancy between variables was 87% on average, so that site variability could be accounted for using 8–28 metrics. In general, flow volume metrics accounted for Axis 1 variability, while coefficients of dispersion had 1.8 times less leverage in Axis 2. With the incorporation into a spatial product and an associated database, this study provides a basis for defining statistically robust reference flow conditions for multiple flow metrics, against which current observed flows at specific sites may be compared.

Spatial Differentiation of the Maximum River Runoff Synchronicity in the Warta River Catchment, Poland

Based on daily flows recorded in the period 1971–2010, the synchronous occurrence of the annual (AMAXq), winter (WMAXq), and summer (SMAXq) maximum specific runoffs in 39 sub-catchments of the Warta River catchment (WRC) in Poland was analyzed. First, trends in the flows were detected using the non-parametric Mann–Kendall (M-K) test. Then, the degree of the synchronous and asynchronous occurrences of the maximum specific runoffs (MAXq) in respective sub-catchments in relation to the Gorzów Wielkopolski gauge closing the WRC was calculated. Finally, the reasons for the detected spatial and temporal differences were discussed. The study revealed a noticeable variability of the analyzed parameters. The highest synchronicity of AMAXq and WMAXq in relation to the closing Gorzów Wielkopolski gauge was revealed in the man-made Kościański and Mosiński canals and in the sub-catchments of the Noteć, Wełna, and lower Prosna rivers. While compared to AMAXq and WMAXq, the summer maxima showed relatively lower degrees of synchronicity, an increase in the synchronous occurrence of SMAXq in the southern part of WRC, and a decrease in its central part were identified. It was concluded that the stronger synchronicity of WMAXq resulted from the nival regime of the investigated rivers. Consequently, the annual maxima were most often associated with the winter half-year. The detected differences of synchronicity of the annual and seasonal runoffs are conditioned by climate, more specifically by the course of winter and resulting from it snow cover thickness, and also the amount and intensity of rainfall in summer.

Ubiquitous increases in flood magnitude in the Columbia River Basin under climate change

The US and Canada have entered negotiations to modernize the Columbia River Treaty, signed in 1961. Key priorities are balancing flood risk, hydropower production, and improving aquatic ecosystem function while incorporating projected effects of climate change. In support of the US effort, Chegwidden et al. (2017) developed a large-ensemble dataset of past and future daily flows at 396 sites throughout the Columbia River Basin (CRB) and select other watersheds in western Washington and Oregon, generating a large ensemble using state-of-the art climate and hydrologic models. In this study, we use that dataset – the largest now available – to present new analyses of the effects of future climate change on flooding using water year maximum daily flows. For each simulation, flood statistics are estimated from Generalized Extreme Value distributions fit to simulated water year maximum daily flows for 50-year windows of the past (1950–1999) and future (2050–2099) periods. Our results contrast with previous findings: we find that the vast majority of locations in the CRB are estimated to experience an increase in future discharge magnitudes. We show that on the Columbia and Willamette rivers, increases in discharge magnitudes are smallest downstream and grow larger moving upstream. For the Snake River, however, the pattern is reversed, with increases in discharge magnitudes growing larger moving downstream to the confluence with the Salmon River tributary, and then abruptly dropping. We decompose the variation in results attributable to climate and hydrologic factors, finding that climate contributes more variation in larger basins while hydrology contributes more in smaller basins. Equally important for practical applications like flood control rule curves, the seasonal timing of flooding shifts dramatically on some rivers (e.g., on the Snake, 20th century floods occur exclusively in late spring, but by the end of the 21st century some floods occur as early as December) and not at all on others (e.g. the Willamette).