In this paper, we propose a new method for estimating the snowmelt degree-day factor (DDFS) directly from MODIS snow covered area (SCA) and ground-based snow depth data without calibration. Snow density is estimated as the ratio between observed precipitation and changes in the snow volume for days with snow accumulation. DDFS values are estimated as the ratio between changes in the snow water equivalent and difference between the daily temperature and a threshold value for days with snowmelt.

This paper shows an interdisciplinary effort for a common methodology on flood risk analysis: hydraullics, hydrology, climatology and meteorology. Most basic problems of work with historical information are faced. Firsts results of data collection on historical floods for Catalonia (Ne Spain) are showed for period AD 1035-2014.

Many previous studies have used stream gauge data to estimate patterns of river width and depth based on variations in river discharge. However, these relationships may not capture all of the actual variability in width and depth. We have instead mapped the widths of all of the rivers wider than 100 m (and many narrower) in the Mississippi Basin and then used them to also improve estimates of depth as well. Our results show width and depth variations not captured by power-law relationships.

We use a hydrologic model coupled with a stream temperature model and downscaled general circulation model outputs to explore changes in stream temperature in the Columbia River basin for the late 21st century. On average, stream temperatures are projected to increase 3.5 °C for the spring, 5.2 °C for the summer, 2.7 °C for the fall, and 1.6 °C for the winter. Our results capture the important, and often ignored, influence of hydrological processes on changes in stream temperature.

A Monte Carlo approach, combining rainfall-stochastic models and hydrological and slope stability physically based models, is used to derive rainfall thresholds of landslide triggering. The uncertainty in threshold assessment related to variability of rainfall intensity within events and to past rainfall (antecedent rainfall) is analyzed and measured via ROC-based indexes, with a specific focus dedicated to the widely used power-law rainfall intensity-duration (I-D) thresholds.

This research article uses of radiogenic isotopes, stable isotopes and groundwater geochemistry to study groundwater age and recharge processes in the Gellibrand Valley, a relatively unstudied catchment and potential groundwater resource. The valley is found to contain both "old", regionally recharged groundwater (300-10,000 years) in the near-river environment, and modern groundwater (0-100 years old) further back on the floodplain. There is no recharge of the groundwater by high river flows.

Western Pacific SST gradients influence eastern East African precipitation in predictable ways. At seasonal and decadal timescales, warm equatorial western Pacific SSTs and cool eastern Pacific SSTs reduce precipitation in East Africa. The gradient between these regions can be used to make reasonably accurate forecasts in one of the world's most food-insecure regions. Recent warming in the western Pacific and stationary eastern Pacific conditions have produced large precipitation declines.

Regional French agricultural yield statistics are used to benchmark root water uptake representations in the ISBA-A-gs model. Key model parameters governing the inter-annual variability of the simulated biomass are retrieved. A complex multi-layer soil hydrology model does not outperform a simple bulk root-zone reservoir approach. This could be explained by missing processes/information in the model such as hydraulic redistribution and detailed soil properties.

Long-term average water and energy cycles are described for two main land cover types in the cultivated Sahel (millet crop and fallow bush). Mean seasonal cycles and annual budgets for all component variables were estimated from detailed field and model analysis. Evapotranspiration totals over 80% of rainfall for both covers, but with different time distribution and soil/plant contributions. The remainder is shared between runoff and deep drainage for the crop, but is only runoff for the fallow.

Our virtual water network of the Roman World shows that virtual water trade and irrigation provided the Romans with resilience to interannual climate variability. Virtual water trade enabled the Romans to meet food demands from regions with a surplus. Irrigation provided stable water supplies for agriculture, particularly in large river catchments. However, virtual water trade also stimulated urbanization and population growth, which eroded Roman resilience to climate variability over time.

Freshwater ecosystems encompass the most threatened species on earth. Environmental flow requirements need to be addressed globally to provide sufficient water for humans and nature. We present a comparison of five environmental flow methods validated with locally calculated EFRs. We showed that methods based on monthly average flow such as the variable monthly flow method are more reliable than methods based on annual thresholds. A range of EFRs was calculated for large river basins.

This paper evaluates three improvements to an energy balance snowmelt model aimed to represent snow surface temperature while retaining the parsimony of a single layer. Surface heat flow is modeled using a forcing term related to the vertical temperature difference and a restore term related to the temporal gradient of surface temperature. Adjustments for melt water refreezing and thermal conductivity when the snow is shallow are introduced. The model performs well at the three test sites.

The paper presents a methodology for using global precipitation products from satellite remote sensing to error-correct and downscale global atmospheric reanalysis precipitation data sets. It is shown that streamflow simulations from the satellite-adjusted precipitation reanalysis give similar statistics to the ones derived by high-resolution ground-based radar rainfall data sets. This approach can be applied globally to derive improved flood frequency maps over data-poor areas.

Periodic flooding of rivers should result in increased groundwater recharge near rivers and thus - younger and fresher groundwater near rivers. This study found the age and salinity of shallow groundwater to increase with proximity to the Tambo River in South East Australia. This appears to be due to the upwelling of older, regional groundwater closer the river. Other chemical parameters are consistent with this. This is a process that may be occurring in other similar river systems.

We projected potential hydrochemical responses in four neighbouring catchments to a range of future climates. The highly variable responses in streamflow and total phosphorus (TP) were governed by geology and flow pathways, where larger catchment responses were proportional to greater soil clay content. This suggests clay content might be used as an indicator of catchment sensitivity to climate change, and highlights the need for catchment-specific management plans.

In this study, topography is considered as a proxy for the variability of most of the catchment characteristics. The model study suggests that classifying the catchments into different runoff production areas based on topography and including the impermeable rocky areas separately in the modeling process mimics the rainfall–runoff process in the Upper Blue Nile basin well and yields a useful result for operational management of water resources in this data-scarce region.

A new hybrid approach was developed to reduce the computational burden of the spin-up procedure by using a combination of model simulations and an empirical depth-to-water table function. Results illustrate that the hybrid approach reduced the spin-up period required for an integrated groundwater--surface water--land surface model (ParFlow.CLM) by up to 50%. The methodology is applicable to other coupled or integrated modeling frameworks when initialization from an equilibrium state is required.

This paper presents a new 12-year glacier meteorological, mass balance, and run-off record from the Canadian Rocky Mountains. This provides insight into the glaciohydrological regime of the Rockies. For the period 2002-2013, about 60% of glacier meltwater run-off originated from seasonal snow and 40% was derived from glacier ice and firn. Ice and firn run-off is concentrated in the months of August and September, at which time it contributes significantly to regional-scale water resources.

We quantified the hydrologic impacts of climate change in the Rio Mannu basin (472.5 km2), Sardinia, Italy. We created high-resolution climate forcings for a physically based distributed hydrologic model by combining four climate models with two statistical downscaling tools of precipitation and potential evapotranspiration. A significant diminution of mean annual runoff at the basin outlet (mean of -32%), and a reduction of soil water content and actual evapotranspiration are expected.

A set of high spatial and temporal satellite images have been used to spatially calibrate crop growth within an agro-hydrological model dedicated to nitrogen contamination of stream water. This type of spatial calibration greatly improved the simulation of nitrogen plant uptake and better constrained nutrient fluxes in the river. This is an example of the benefit of the forthcoming Sentinel-2 high resolution optical image series that will be acquired every 4/5 days over continental surfaces.

This study demonstrates the effectiveness of winter cover crops for reducing nitrate loads using the Soil and Water Assessment Tool (SWAT). It illustrates the following: (1) nitrate removal efficiency varies greatly by species, timing, and extent of winter cover crop implementation; and (2) nitrate exports vary based on edaphic and agronomic characteristics of the croplands upon which crops are planted.

The characteristics of the macropore network determine the potential for fast transport of solutes through soil. Such characteristics computed from 3-dimensional X-ray tomography images were combined with measured solute breakthrough curves and near-saturated hydraulic conductivities. At a given flow rate, smaller macroporosities, poorer local connectivity of the macropore network and smaller near-saturated hydraulic conductivities resulted in a greater degree of preferential transport.

Hydrological modeling and assessment tools were used to provide evidence of the expected hydrological alterations that hydropower development in the lower Mekong tributaries could bring to the Tonle Sap. The most significant alterations are in terms of water levels during the dry season and rates of water level rise/drop which are crucial for tree seed germination and fish migrations, and therefore major ecological disruptions are likely to follow.

Climate change simulations project drought to increase even under moderate warming scenarios; both droughts and floods increase sharply with severe warming. Over 20% of the globe is projected to experience reduced rainfall but greater year-to-year variability. The vulnerability of growing regions for many types of crops are assessed based on soil moisture, and rivers using runoff projections. Increased water cycle variability is found to be a threat to agriculture and river systems as well.

We present a method to define hydrological landscape units by a time series of thermal infrared satellite data. Land surface temperature is calculated for 28 images in 12 years for a catchment in Luxembourg. Pattern measures show spatio-temporal persistency; principle component analysis extracts relevant patterns. Functional units represent similar behaving entities based on a representative set of images. Resulting classification and patterns are discussed regarding potential applications.

This study demonstrates the processes by which instantaneous longitudinal water temperature gradients may be generated in a stream reach that transitions from moorland to semi-natural forest in the absence of substantial groundwater inflows. Water did not cool as it flowed downstream. Instead, temperature gradients were generated by a combination of reduced rates of heating in the forested reach and advection of cooler (overnight and early morning) water from the upstream moorland catchment.

This paper presents measurements of the balance of water inputs and outputs over 1 year for a river basin in the Andes of Peru. Our results show that the annual water budget is balanced within a few percent uncertainty; that is to say, the amount of water entering the basin was the same as the amount leaving, providing important information for understanding the water cycle. We also show that seasonal storage of water is important in sustaining the flow of water during the dry season.

This paper proposes a methodology, shaped by the EU Flood Directive, for the integrated assessment of flood risk at the regional scale for multiple receptors (i.e. people, economic activities, natural and semi-natural systems and cultural heritage) based on the subsequent assessment of hazards, exposure and vulnerability. By means of MCDA and GIS tools, it supports the ranking of the area, sub-areas and hotspots at risk, in order to evaluate the benefits of different risk prevention scenarios.