We investigate how rivers in a flash-flood-prone region in southern France respond to rainfall depending on initial soil moisture. Therefore, high-resolution data of rainfall, river discharge and soil moisture were used. We find that during dry initial conditions, the rivers hardly respond even for heavy rain events, but for wet initial conditions, the response remains unpredictable: for some rain events almost all rainfall is transformed to discharge, whereas this is not the case for others.

Karst aquifers are vulnerable to pollution due to the typically short particle travel times. As the rainwater runs off on the surface it may collect contamination before infiltrating. This paper proposes a new field-mapping method for the ability of the landscape to produce and convey surface runoff. The method is based on local data collection in the field, and a visual assessment of surface runoff traces from a distance, which makes it suitable for larger areas than traditional field mapping.

The hyporheic zone is the area below riverbeds where surfacewater and groundwater mix. Hyporheic flow is linked to river processes and functions, but research to date has not sufficiently addressed how factors operating at different scales in time and space drive hyporheic flow variations at reach and larger scales. This review presents the scale-specific processes and interactions that control hyporheic flow, and a case study showing how valley factors affect its expression at the reach scale.

Understanding responses by changes in land use and land cover (LULC) and climate over the past decades on streamflow in the upper Blue Nile River basin is important for water management and water resource planning. Streamflow in the UBNRB has shown an increasing trend over the last 40 years, while rainfall has shown no trend change. LULC change detection findings indicate increases in cultivated land and decreases in forest coverage prior to 1995.

Due to the lack of long-term observations, insights into changes of groundwater resources are obscured. In this paper we assess past and potential future changes in groundwater drought in headwater catchments using a baseflow approach. There are a few past trends which are highly dependent on the period of analysis. Catchments with short response times are found to have a higher sensitivity to projected seasonal precipitation shifts, urging for a local management based on response times.

Description of thermal regimes in flowing waters is key to understanding physical processes and improving bioassessments, but has been limited by sparse data sets. Using a large annual temperature data set from a mountainous area of the western U.S., we explored thermal regimes using principle component analysis. A small number of summary metrics adequately represented most of the variation in this data set given strong temporal coherence among sites.

The paper presents groundwater storage conditions in all the major river basins across Alberta, Canada. We used remote-sensing data and investigate their performance using available ground-based data of groundwater level monitoring, storage coefficients, aquifer thickness, and surface water measurements. The water available for groundwater recharge has been studied in detail. Separate approaches have been followed for confined and unconfined aquifers for estimating groundwater storage.

This paper evaluates several schemes for post-processing monthly and seasonal streamflow forecasts using the Australian Bureau of Meteorology's streamflow forecasting system. Through evaluation across 300 catchments, the best-performing scheme has been identified, which is found to substantially improve important aspects of the forecast quality. This finding is significant because the improved forecasts help water managers and users of the service to make better-informed decisions.

This paper reports the results of field surveys conducted in Lake Issyk-Kul in 2015–2017 and compares the present-day data with the available historical records. Our data do not confirm the reports of progressive warming of the deep Issyk-Kul waters as suggested in some previous publications. However, they do indicate a positive trend of salinity in the lake’s interior over the last 3 decades. An important newly found feature is a persistent salinity maximum at depths of 70–120 m.

This study assesses the combined impacts of climate change and socio-economic developments on the future water gap for the Indus, Ganges, and Brahmaputra river basins until the end of the 21st century. The results show that despite projected increases in surface water availability, the strong socio-economic development and associated increase in water demand will likely lead to an increase in the water gap, indicating that socio-economic changes will be the key driver in the evolving water gap.

In recent years, surpluses of desalinated seawater (DSW) are stored in the Israeli coastal aquifer. We monitor DSW spread in the aquifer using the difference between isotope composition of reverse-osmosis DSW and natural fresh water, which simplifies the system to two distinct end-members. A hydrogeological flow and transport model is used to demonstrate the robustness of this simplification, predict the future spread of DSW in the aquifer and mixing in wells, and estimate DSW recovery efficacy.

From a classification of river discharge, the effective or dominant discharge is the one whose class corresponds to the maximum sediment supply. The efficiency of the Wadi Sebdou (NW Algeria) was examined over 1973–2004. Two subdivisions allowed a correct distribution of frequencies and supplies of water and sediments. Their effective discharge, close to the half-load discharge, was compared to analytical values based on statistics and rating curves. Return periods were also explained.

This paper uses a unique observational dataset of a tropical African lake (L. Kivu) to assess the effect of rain on lake surface temperature. Data from 4 years were categorised by daily rain amount and total net radiation to show that heavy rain may reduce the end-of-day lake temperature by about 0.3 K. This is important since lake surface temperature may influence local weather on short timescales, but the effect of rain on lake temperature has been little studied or parametrised previously.

This research is paramount given the significance of karst aquifers as essential drinking water sources. While CBZ is considered conservative, CAF is subject to sorption and degradation, and therefore each of these two pollutants can be considered effective tracers for specific assessment of aquifer contamination. The model presented in this paper shows how each of the mentioned contaminants could serve as a better tool for aquifer contamination characterization and its treatment.

Brook trout are known to seek out groundwater-discharge zones for spawning. However, in a groundwater-dominated system, we observed trout using a few locations for repeatedly laying eggs. To improve the management of this cold-water species, we wanted to know why these specific groundwater-discharge zones were desirable. Through a combination of geophysical and chemical measurements, we found that locations where the stream intersects the sandy valley wall create oxygen-rich seepage zones.

Analyses of run lengths of Pacific decadal variability (PDV) suggest that there is no significant difference between run lengths in positive and negative phases of PDV and that it is more likely than not that the PDV run length has been non-stationary in the past millennium. This raises concerns about whether variability seen in the instrumental record (the last ~100 years), or even in the shorter 300–400 year paleoclimate reconstructions, is representative of the full range of variability.

We quantify net intercatchment groundwater flows in the Meuse basin in a complementary three-step approach through (1) water budget accounting, (2) testing a set of conceptual hydrological models and (3) evaluating against remote sensing actual evaporation data. We show that net intercatchment groundwater flows can make up as much as 25 % of mean annual precipitation in the headwaters and should therefore be accounted for in conceptual models to prevent overestimating actual evaporation rates.

Satellite-based river gauging can be constructed based on remote-sensing-derived surface water extent and modelled discharge, and used to estimate river discharges with satellite observations only. This provides opportunities for monitoring river discharge in the absence of a real-time hydrological model or gauging stations.

Our study improved a global-scale groundwater model to build the first nationwide estimate of the water table surface in New Zealand. By identifying the main alluvial aquifers with high spatial detail, we showed that this model can help better delineate aquifer boundaries. In catchment studies we demonstrated excellent correlation with ground observations and provided water table estimates where data were sparse and across regions, which could help solve trans-boundary issues between catchments.

Effects that climate change could have on the Tajo–Segura transfer are evaluated. To that, water resources that would be in the donor basin are estimated by hydrological modelling if the last climatic projections are accomplished. For these water resources, the exploitation of the transfer is simulated using a decision support system, providing volumes that could be transferred to the Segura basin according to its operating rule.

We have discovered transient appearances of strong turbulent mixing beneath the ice of an Arctic lake. Such mixing events increase heating of the ice base up to an order of magnitude and can significantly accelerate ice melting. The source of mixing was identified as oscillations of the entire lake water body triggered by strong winds over the lake surface. This previously unknown mechanism of ice melt may help understand the link between the climate conditions and the seasonal ice formation.

The potential of rain to cause soil erosion by runoff is called rain erosivity. Rain erosivity is highly variable in space and time even over distances of less than 1 km. Contiguously measured radar rain data depict for the first time this spatio-temporal variation, but scaling factors are required to account for differences in spatial and temporal resolution compared to rain gauge data. These scaling factors were obtained from more than 2 million erosive events.

This study investigates the use of gauge precipitation and air temperature observations to ascertain radar precipitation in cold climates. The use of air temperature as an additional variable in a non-parametric model improved the estimation of radar precipitation significantly. Further, it was found that the temperature effects became insignificant when air temperature was above 10 °C. The findings from this study could be important for using radar precipitation for hydrological applications.

One of the critical issues in MPS simulation is the difficulty in obtaining a credible 3-D training image. We propose an MPS-based 3-D reconstruction method on the basis of 2-D cross sections, making 3-D training images unnecessary. The main advantages of this approach are the high computational efficiency and a relaxation of the stationarity assumption. The results, in comparison with previous MPS methods, show better performance in portraying anisotropy characteristics and in CPU cost.

A novel distribution function is proposed for describing the spatial distribution of soil water storage capacity, and then the classical and empirical hydrologic model (the SCS curve number method) is derived as when the initial soil water storage is zero. This distribution function unifies the SCS curve number method and probability-distributed models such as the VIC and Xinanjiang models. The unified model provides a better way for modeling surface runoff.

DOC and DIC export in Taiwan shows that the annual DOC and DIC fluxes were 2.7–4.8 and 48.4–54.3 ton C km² yr¹, respectively, which were approximately 2 and 20 times higher than the global means of 1.4 and 2.6 ton C km² yr¹, respectively.

The present study evaluates the skill of a seasonal forecasting system for hydrological relevant variables in Denmark. Linear scaling and quantile mapping were used to correct the forecasts. Uncorrected forecasts tend to be more skillful than climatology, in general, for the first month lead time only. Corrected forecasts show a reduced bias in the mean; are more consistent; and show a level of accuracy that is closer to, although no higher than, that of ensemble climatology, in general.

Of particular interest to NASA's SMAP-based agricultural applications is a monitoring product that assesses near-surface soil moisture in terms of probability percentiles for dry and wet conditions. However, the short SMAP record length poses a statistical challenge for the meaningful assessment of its indices. This study presents initial insights about using SMAP Level 3 and Level 4 for monitoring drought and pluvial regions with a first application over the contiguous United States (CONUS).