Investigation of Spatial and Temporal Variability of Hydrological Drought in Slovenia Using the Standardised Streamflow Index (SSI)

Drought is a complex phenomenon with high spatial and temporal variability. Water scarcity has become a growing problem in Slovenia in recent decades. Therefore, the spatial and temporal variability of hydrological drought was investigated in this study by analysing the Standardized Streamflow Index (SSI). Monthly discharge data series from 46 gauging stations for the period 1961–2016 were used to calculate SSI values at five different time scales (1, 3, 6, 12, and 24 months). The results indicate that the frequency and intensity of droughts in Slovenia has increased in recent decades at most of the analysed gauging stations and at all time scales considered. Spring and summer periods were identified as critical in terms of water deficit. SSI values vary independently from the location of the gauging station, confirming that drought is a regional phenomenon, even in a small country such as Slovenia. However, SSI values vary considerably depending on the time scale chosen. This was also confirmed by the results of the hierarchical clustering of the number of extreme droughts, as various time scales resulted in a different distribution of gauging stations by individual groups.

Streamflow Changes of Small and Large Rivers in the Aldan River Basin, Eastern Siberia

The flow of large northern rivers has increased, but regional patterns of changes are not well understood. The aim of this study is the estimation of monthly discharge changes of the 11 river catchments in the Aldan River basin in Eastern Siberia, the largest Lena River tributary and the sixth largest river in Russia. We considered the trend dependence on month, number of years in the sample, finish and start years, and basin area. The median fraction of samples with no trend, positive and negative trends are 70.5%, 28.5%, and 1%, respectively. Longer samples tend to show more positive trends than shorter ones. There is an increasing fraction of samples with positive trends as a function of later sample end year, whereas the start year does not result in a similar pattern. The larger basins, with one exception, have more positive trends than smaller ones. The trends in monthly streamflow have prominent seasonality with absence of positive trends in June and increasing fraction of samples with positive trends from October till April. The study reports the recent streamflow changes on the rarely analyzed rivers in Eastern Siberia, where air temperature rises faster than in average on the globe. The study results are important for water resources management in the region and better understanding of current environmental changes.

Effect of Discharge on Water Quality in Euphrates River Between Hit and Ramadi, Iraq

The objective of this study was to determine the relationship between water drainage rates in Hit and Ramadi cities and the water quality of the Euphrates River. The studied area of Euphrates River extends from Hit to Ramadi, where two sampling stations were selected monthly in 2012, 2013, and 2018. The results indicate variations and decreasing in the monthly discharge rate of the study period; the year 2012 had higher discharge rate values than 2013, which in turn was higher than in 2018, for both gauging stations. Our results indicate that with decreasing discharge trends, some selected water quality parameters had an increasing trend. During the selected years, there was an increase in levels of sulfate, nitrate, dissolved oxygen, magnesium, and turbidity in the Ramadi station compared to the Hit station, as the rate of discharge of the river increases in the former. A positive significant correlation between discharge rate and dissolved oxygen and dissolved solids were reported. The Haditha Dam and its reservoir affect the downstream discharge rate and in turn the water quality at Hit and Ramadi Cities.

Simulation Model for Optimal Operation of Dokan Dam Reservoir Northern of Iraq

Due to the limitation of water renewable resources on one hand and increasing growth in consuming water in different parts such as agriculture, industry, urban, and the environment in other hand, face management of these valuable resources to many challenges. Present study attempts to clarify recent condition of the problem and introduce effective management tools in water supply sector. In order to achieve this purpose, simulating model HEC-Res Sim was used for Dokan Dam to study the operational behavior of the reservoir and to investigate the model capability in representing and simulating the real system. The study based on monthly discharge data for the period from 1986 to 2016 measured at the inlet of Dokan Dam reservoir. The results of the current study were compared and evaluated against those counterparts observed data using two statistical metrics, correlation coefficient and Nash- Sutcliff coefficient efficiency. Moreover, an empirical formula was found linking the amount of inflow to the reservoir with the amount of outflow. The results showed that the HEC-ResSim 3.0 performed well in simulating the monthly discharges. Therefore, HEC-ResSim 3.0 could be used for better water system analysis in this study area.

PENGARUH PERUBAHAN TUTUPAN LAHAN TERHADAP ALIRAN PERMUKAAN PADA SUB DAS KAMPAR KANAN

Kampar watershed has a length of 580 km, with a catchment area of 21,086 km2, a maximum discharge of 2,200 m3 / s, a minimum discharge of 49 m3 / s. The largest level of damage in 4 major watersheds in Riau Province is located in the Kampar watershed, reaching 5,986 hectares. This study aims to analyze the effect of changes in land cover on surface runoff in the right sub-watershed using SWAT (hydrological model (soil water assessment tool). From the research results, changes in land use from 2009 to 2018 tend to increase precipitation from 3866.33 mm to 4687.94. Significant changes occurred in the water yield or the total amount of water entering the main river during the simulation period from 1722.65 mm to 3633.75 mm. The results of the calibration using the monthly discharge data from 2010 - 2011, the results of observations and predictions on the Lake Bingkuang SPAS were 276.70 m3 / s and 354.98 m3 / s. The results of the validation using the monthly discharge data for 2018 are 115.63 m3 / s and 93.03 m3 / s. The weight value and score of each performance of the right Kampar Sub-watershed in 2009 - 2018 shows that the percentage of vegetation cover (PPV) with a weight of 20%, a score of 0.5. Flow Regim Coefficient with a weight of 5%, a score of 0.75, while the annual flow coefficient with a weight of 5%, score, 0.5. The total number of watershed performance assessments with a weight of 30%, a score of 1.75, and the results of the assessment is 16.25 so that the performance results of the right Kampar Sub-watershed is 0.54.

PISCO_HyM_GR2M: A Model of Monthly Water Balance in Peru (1981–2020)

Quantification of the surface water offer is crucial for its management. In Peru, the low spatial density of hydrometric stations makes this task challenging. This work aims to evaluate the hydrological performance of a monthly water balance model in Peru using precipitation and evapotranspiration data from the high-resolution meteorological PISCO dataset, which has been developed by the National Service of Meteorology and Hydrology of Peru (SENAMHI). A regionalization approach based on Fourier Amplitude Sensitivity Testing (FAST) of the rainfall-runoff (RR) and runoff variability (RV) indices defined 14 calibration regions nationwide. Next, the GR2M model was used at a semi-distributed scale in 3594 sub-basins and river streams to simulate monthly discharges from January 1981 to March 2020. Model performance was evaluated using the Kling–Gupta efficiency (KGE), square root transferred Nash–Sutcliffe efficiency (NSEsqrt), and water balance error (WBE) metrics. The results show a very well representation of monthly discharges for a large portion of Peruvian sub-basins (KGE ≥ 0.75, NSEsqrt ≥ 0.65, and −0.29 < WBE < 0.23). Finally, this study introduces a product of continuous monthly discharge rates in Peru, named PISCO_HyM_GR2M, to understand surface water balance in data-scarce sub-basins.

Satellite altimeter to estimate discharge of the Ganga River

&lt;p&gt;We use satellite altimeter data to estimate average monthly discharge at seven different locations in the middle and lower parts of the Ganga River. We have obtained the water level from different satellite altimeter mission ERS-2 (1995 - 2007), Envisat (2002 - 2010), and Jason-2 (2008 - 2017) through publicly available databases Hydroweb and DAHITI. To make the water level comparable with the gauge stations, we applied the datum and offset correction to the altimetry datasets. The corrected water level data well accord with the ground measurements with RMSE values in a range between (22 - 71) cm.&amp;#160;&lt;/p&gt;&lt;p&gt;We then established stage-discharge rating curves from the water-level derived from satellite altimeter and the corresponding discharge measured at the nearest gauge station. We use these rating curves to estimate discharge of the Ganga River in the middle (Kachla bridge, Kanpur, Shahzadpur, Prayagraj and Mirzapur) and lower (Azmabad and Farakka) reaches from the water-level from satellite altimeter. Our estimates of discharge compare with the monthly average discharge recorded at the nearest ground station.&lt;/p&gt;&lt;p&gt;We observed that the uncertainty in the discharge estimate is relatively high in the middle than the lower reaches of the Ganga River. This is probably associated with the low discharge and shallow flow depth of the Ganga River in the middle reaches as compare to the high flow depth and discharge in the lower reaches. Overall performance analysis of statistical parameters (NSE, RSR, PBIAS, and R&lt;sup&gt;2&lt;/sup&gt;), suggests that except for the Kanpur station, our estimates of discharge can be categories into &quot;good&quot; to &quot;satisfactory&quot;.&lt;/p&gt;

Quantifying the Uncertainty of the Future Hydrological Impacts of Climate Change: Comparative Analysis of an Advanced Hierarchical Sensitivity in Humid and Semiarid Basins

Comparison and quantification of different uncertainties of future climate change involved in the modeling of a hydrological system are highly important for both hydrological modelers and policy-makers. However, few studies have accurately estimated the relative importance of different sources of uncertainty at different spatiotemporal scales. Here, a hierarchical sensitivity analysis framework (HSAF) incorporated with a variance-based global sensitivity analysis is developed to quantify the spatiotemporal contributions of different uncertainties in hydrological impacts of climate change in two different climatic (humid and semiarid) basins in China. The uncertainty sources include three emission scenarios (ESs), 20 global climate models (GCs), three hydrological models (HMs), and the associated sensitive hydrological parameters (PAs) screened and sampled by the Morris and Latin hypercube sampling methods, respectively. The results indicate that the overall trend of uncertainty is PA > HM > GC > ES, but their uncertainties have discrepancies in projections of different hydrological variables. The HM uncertainty in annual and monthly discharge projections is generally larger than the PA uncertainty in the humid basin than semiarid basin. The PA has greater uncertainty in extreme hydrological event (annual peak discharge) projections than in annual discharge projections for both basins (particularly for the humid basin), but contributes larger uncertainty to annual and monthly discharge projections in the semiarid basin than humid basin. The GC contributes larger uncertainty in all the hydrological variables projections in the humid basin than semiarid basin, while the ES uncertainty is rather limited in both basins. Overall, our results suggest there is greater spatiotemporal variability of hydrological uncertainty in more arid regions.

The Influence of Watershed Morphometry to River Discharge Variation (Case Study of Bengkulu Watershed, Indonesia)

Morphometric analysis in a watershed is a requirement in analyzing hydrological conditions in a watershed, because the properties of river networks and their relationship to each other will affect the condition of water resources in the watershed. This study aims to analyze the variations in the discharge of two rivers in the upper Bengkulu watershed and the morphometric aspects that influence it. For this reason, several morphometric aspects are calculated, such as the area of the watershed, circulation ratio, median elevation and slope. The results showed that the Rindu Hati River had a higher monthly discharge than the Susup River. The sizeable difference in discharge between the Rindu Hati and Susup Rivers is due more to differences in the size of the area. As is known, the total area of the Rindu Hati Sub-watershed is 184.2 km2, while the Susup Sub-watershed is 103.6 km2. With a large area, the Rindu Hati Subwatershed will be able to accommodate a large amount of rainwater as well.