After soil gets wet, much of the surface moisture evaporates directly back into the air. Recent satellite data show that this process is enhanced when there is more water in the soil, less humidity in the air, and less vegetation covering the ground. A widely used model shows similar effects of soil water and humidity, but it largely misses the role of vegetation and assigns outsized importance to soil type. These results are encouraging evidence that the satellite can be used to improve models.

The paper presents major milestones in the transformation of hydrologic science over the last 50 years from engineering hydrology to Earth system science. This transformation has involved a transition from a focus on time (empirical) to space (Newtonian mechanics), and to time (Darwinian co-evolution). Hydrology is now well positioned to again return to a focus on space or space–time and a move towards regional process hydrology.

Laboratory experiments using water-filled sand and gravel samples with significant contents of iron oxide coatings were performed to identify the relationship between effective hydraulic radius and nuclear magnetic resonance (NMR) response. Our interpretation approach for the NMR data leads to reliable estimates of hydraulic conductivity without calibration, but is limited to coarse material for physical reasons. An NMR-based observation system for iron clogging in boreholes is planned.

River flow regimes are being altered by global change. Understanding the mechanisms behind such alterations is crucial for hydrological prediction. We introduce a novel interpretation of river flow metrics (scaling) that allows any river basin to be classified as regulated or unregulated, and to identify transitions between these states. We propose the forest reservoir hypothesis to explain how forest loss can force the Amazonian river basins from regulated to unregulated states.

We characterized drought by linking climate anomalies with the change in precipitation–runoff relationships in China's Loess Plateau, where drought is of major concern for revegetation. Multi-year drought causes a change in the precipitation–runoff relationship in this water limited area. The drought causing a decrease in runoff ratio is vital to ecosystem management. The revegetation in the Loess Plateau should live with the spatially varied drought.

This paper describes instances in the Grand Canyon study area and a laboratory experiment in which very high suspended-sediment concentrations result in incorrectly low turbidity recorded with a commonly used field instrument. If associated with the monitoring of a construction or dredging project, false low turbidity could result in regulators being unaware of environmental damage caused by the actually much higher turbidity.

Long-term hydrological predictions are important for water management planning, but are also prone to uncertainty. This study investigates three sources of uncertainty for long-term hydrological predictions in the US: climate models, hydrological models, and hydrological model parameters. Mapping the results revealed spatial patterns in the three sources of uncertainty: different sources of uncertainty dominate in different regions.

This study investigates global patterns relating urban river flood impacts to socioeconomic development and changing hydrologic conditions, and comparisons are provided between 98 individual cities. This paper condenses and communicates large amounts of information to accelerate the understanding of relationships between local urban conditions and global processes, and to potentially motivate knowledge transfer between decision-makers facing similar circumstances.

We present a new approach to improve the water storage estimate. Our approach combines GRACE's raw data (least-squares normal equation) with the results from the Community Atmosphere Land Exchange (CABLE) model. No post-processing filter is applied to GRACE data, and the full GRACE signal and error information are exploited. The approach is applied over 10 Australian river basins, and the evident improvement of the water storage estimate, particularly groundwater component, is clearly observed.

We investigate the relative roles of statistical weather preprocessing and streamflow postprocessing in hydrological ensemble forecasting at short- to medium-range forecast lead times (day 1–7). For this purpose, we develop and implement a regional hydrologic ensemble prediction system (RHEPS). Overall analysis shows that implementing both preprocessing and postprocessing ensures the most skill improvements, but postprocessing alone can often be a competitive alternative.

Effective monitoring and prediction of flood and drought events requires an improved understanding of surface water dynamics. We examined how the relationship between surface water extent, as mapped using Landsat imagery, and climate, is a function of landscape characteristics, using the Prairie Pothole Region and adjacent Northern Prairie in the United States as our study area. We found that at a landscape scale wetlands play a key role in informing how climate extremes influence surface water.

We modeled hydrological changes under impacts of large-scale dike constructions for intensive rice production in the floodplain of the Vietnamese Mekong Delta. Four scenarios show a significant increase in peak water levels in the upstream rivers, but very few water level changes are found downstream. Water balance calculations show where the floodwater goes under four dike construction scenarios. Its impacts on the tidal areas need to be clarified in the future with a 3-D hydraulic model.

This paper provides the connection between two simple equations describing groundwater flow at different scales: the Darcy equation describes groundwater flow at pore scale, the linear reservoir equation at catchment scale. The connection between the two appears to be very simple. The two parameters of the equations are proportional, depending on the porosity of the subsoil and the resistance for the groundwater to enter the surface drainage network.

This study used a portable 56-sensor, 3-D temperature array with three heat pulse sources to measure the flow direction and magnitude below the water–sediment interface. Breakthrough curves from each of the sensors were analyzed using a heat transport equation. The use of short-duration heat pulses provided a rapid, accurate assessment technique for determining dynamic and multi-directional flow patterns in the hyporheic zone and is a basis for improved understanding of biogeochemical processes.

Surface soil moisture was retrieved from a grassland site in southwestern France using the GNSS-IR technique. In order to efficiently limit the impact of perturbing vegetation effects, the grass growth period and the senescence period are treated separately. While the vegetation biomass effect can be corrected for, the litter water interception influences the observations and cannot be easily accounted for.

Topography plays an important role in determining the spatial heterogeneity of ecological, geomorphological, and hydrological processes. Topography plays a more dominant role in low flows than high flows. Our analysis also identified five significant TIs: perimeter, slope length factor, surface area, openness, and terrain characterization index. These can be used to compare watersheds when low flow assessments are conducted, specifically in snow-dominated regions.

The output from numerical weather prediction (NWP) models is known to have errors. River forecast centers in Canada mostly use precipitation forecasts directly obtained from American and Canadian NWP models. In this study, we evaluate the forecast performance of ensembles generated by a Bayesian post-processing approach in cold climates. We demonstrate that the post-processing approach generates bias-free forecasts and provides a better picture of uncertainty in the case of an extreme event.

China has suffered some of the effects of global warming, and one of the potential implications of climate warming is the alteration of the temporal–spatial patterns of water resources. In this paper, the Budyko-based elasticity method was used to investigate the responses of runoff to historical and future climate variability over China at both grid and catchment scales. The results help to better understand the hydrological effects of climate change and adapt to a changing environment.

A new method is proposed to solve the stochastic unsteady open-channel flow system in only one single simulation, as opposed to the many simulations usually done in the popular Monte Carlo approach. The derivation of this new method gave a deterministic and linear Fokker–Planck equation whose solution provided a powerful and effective approach for quantifying the ensemble behavior and variability of such a stochastic system, regardless of the number of parameters causing its uncertainty.

A newly proposed method is applied to solve a stochastic unsteady open-channel flow system (with an uncertain roughness coefficient) in only one simulation. After comparing its results to those of the Monte Carlo simulations, the new method was found to adequately predict the temporal and spatial evolution of the probability density of the flow variables of the system. This revealed the effectiveness, strength, and time efficiency of this new method as compared to other popular approaches.

We benchmarked when and where ensemble streamflow prediction (ESP) is skilful in the UK across a diverse set of 314 catchments. We found ESP was skilful in the majority of catchments across all lead times up to a year ahead, but the degree of skill was strongly conditional on lead time, forecast initialization month, and individual catchment location and storage properties. Results have practical implications for current operational use of the ESP method in the UK.

The study examines the impact of higher temperatures expected in a future climate on how rainfall varies with time during severe storm events. The results show that these impacts increase future flood risk in urban environments and that current design guidelines need to be adjusted so that effective adaptation measures can be implemented.