The subsurface is often treated as a black box in hydrologic models. But we are beginning to understand interactions among the land surface, weathering fronts, and the water table that push landscapes toward steady-state morphologies. Weathering fronts that change the porosity act like valves that partition water into shallow- and deep-flowing fractions. These flows then allow fronts for low- and high-solubility minerals, respectively, to advance at the erosion rate. This conceptualization could help to replace the black box when modelling headwater catchments.

Constructed wetlands are frequently used in Germany for communal waste water purification including removal of phosphorus. The investigated filter sands (fluviatile as well as zeolite and clinopyroxene containing lava sands) were mainly accumulating inorganic, poorly crystalline P species, indicating no imminent threat of P saturation. A potentially high desorption capacity points to possible future recycling endeavours or use as soil amendments which needs further research.

Suspended Sediment Fluxes on Arc / Isère Observatory obtained with water discharge and turbidity measurements.

We introduce the freely available web-based Water in an Agricultural Landscape—NUčice Database (WALNUD) dataset at experimental catchment Nučice, the Czech Republic. The datasets consist of observed variables (e.g. measured precipitation, air temperature, stream discharge, and soil moisture) and are available online for public use. The cross-seasonal, open access datasets at this small-scale agricultural catchment will benefit not only hydrologists but also local farmers.

Streamflow is gauged in several sub-catchments of the Baker Creek Research Catchment. The period of record (2003-2019) includes both historic wet and dry periods. These data are helping to improve understanding of hydrological connectivity response to climate cycles in this discontinuous permafrost region dominated by exposed bedrock and lakes.

Informative: Beasley Lake Watershed, influenced by row-crop agriculture, is part of the USDA Conservation Effects Assessment Project (CEAP). The watershed has an archived 25-year long-term database that includes lake hydrology, precipitation, and water quality. The long-term database is available to researchers using a GIS-platform web-based application, Sustaining the Earth's Watersheds, Agricultural Research Data System (STEWARDS) that encompasses spatial and temporal data collected from multiple sites within the watershed.

• The water-hydropower equivalent decreased as the transferred hydropower into the Luanhe River Basin increased;
• A transferred hydropower amount of 22.46 kWh/s, equivalent to 18.30 m³/s conserved water, was optimal for the Luanhe River Basin;
• The conserved water should be distributed to the Luanhe River in the proportions of 0.55:0.1:0.35 during the wet, normal and dry seasons, respectively, which is the optimal scheme to sustain the hydrological processes of the river.

The water and mass balance of the Ciénega de Santa Clara, the most important remnant wetland of the Colorado River Delta, was analysed during 2014–2015. We examined different scenarios of future conditions based on variations of inflow from its principal binational source and the effects of the increase of temperatures in the watershed due to climate change. Maintenance of the Ciénega de Santa Clara's hydrological equilibrium will require at least 5.10 m³ s⁻¹ of water during the summer months.

The changing spatial distribution of the three-year averaged groundwater level (WTD, meter below ground level) during the mid-decade years of the 1980s, 1990s, 2000s, and their comparison with that during 2010–2012.

• Four sites were monitored where beavers have been reintroduced in Great Britain to understand the impacts of beaver dams upon flow attenuation.
• Analysis of >1000 storm events showed an overall trend of reduced total stormflow, increased peak rainfall to peak flow lag times and reduced peak flows.
• Analysis showed flow attenuation impacts due to beaver damming to persist during largest flood events, whilst additionally flow regimes became overall less flashy following beaver impact.

Multiyear evapotranspiration (ET) and potential evapotranspiration (PET) at four boreal fens are estimated, and the effect of net radiation (Rnet), air temperature (Tair), water table depth (WTD), and vapour pressure deficit (VPD) on ET is analyzed.

• Measurements of canopy water balance components are performed in a humid balsam fir boreal forest during the snow-free seasons of 2017 and 2018.
• The rate of change in water volume on the canopy was estimated with water balance and directly measured using stem compression system.
• Evapotranspiration partitioning was estimated with eddy-covariance and sapflow measurements.

Leaf shape and slope have a great impact on the leaf litter interception. The minimum ISC (C_min) of the leaf litter at flat and gentle slopes exceeds that at steep slope. Leaf distribution pattern has a major effect on the leaf litter interception. Flow paths increase the litter drainage and reduce the interception capacity. The maximum ISC (C_max) of the leaf litter decreases with increasing number of flow paths. Leaf distribution patterns in the litter layer. RP, OFP, TFP and THFP represent the random pattern, one flow path, two flow paths and three flow paths, respectively.

A formula for quick estimation of actual evapotranspiration of any crops is suggested. The crop coefiicient is introduced as a function of reference evapotranspiration and relative humidity.

Evaporation (EV) plays an important role in soil drainage. Our analysis showed that the stronger EV is the faster the water reaches deeper depths. Additionally, the smaller the hydraulic conductivity of a soil is the stronger the impact of EV on the drainage of a soil.

Assessments of seasonal stable water isotope trends in a mountain watershed indicate increased connectivity between areas proximal to streams and streamflow during the winter period. The use of a longitudinal sampling scheme provided a mechanism for relating changes in elevation with hillslope-stream connectivity, taking advantage of the isotopic lapse rate of precipitation. Correlations between elevation and δD are strongest during February and March, and weak during July and August, indicating increased transmission of meteoric water during winter and spring, and decreased later in the year.

The hydrogeomorphology of the Vietnamese Mekong Delta has been significantly altered by natural and anthropogenic drivers. By analysing the long-term discharge, water level, sediment, and bathymetric data, supported by a coupled 2D hydro-sediment-morpho dynamics model, we observed that riverbed incision was the main cause of the decreased dry season water levels in the Tien River, although the respective discharges increased. Consequently, the decreased water level was likely one of the main causes of the enhanced salinity intrusion.

Dissolved major ion chemistry of two tropical rivers (Damodar and Subarnarekha) from India has been investigated to constrain solute sources and weathering patterns. High TDS and sulphate concentrations of these rivers are due to intense sulphide oxidation in the mining-dominated regions. The area-normalized sulphide oxidation fluxes in these streams are higher compared to that for global rivers. Chemical weathering in tropical rivers influenced by sulphuric acid, therefore, may release a significant amount of CO₂ into the atmosphere.

• The exact groundwater divide on the water table is delineated as the division point of two local flow systems transporting infiltration water toward two rivers.
• The top of the water table is not the exact groundwater divide and the distance between them can reach up to 8.9% of the distance between rivers.
• The analytical method is applied to the Loess Plateau, China.

The model of nitrogen cycling in the hyporheic zone (HZ) with unsteady flow effects was proposed. An optimal range of river channel gradients for enhancing biogeochemical reactions was found. The nitrate sink-source function transformations of HZ were independent of the flood events. The nitrate removal efficiency during a single-peak flood event was quantified.

Rill flow velocity decreases with increasing thawed soil depth, and the decreasing rate also decreased. Rill flow velocity responds differently to slope gradient and rainfall intensity under different thawed depths. Model was established to estimate rill flow velocity on partially thawed soil slopes.

We investigated how much the choice of calibration period can affect water balances in Soil and Water Assessment Tool models of three United States watersheds. We found that this choice can cause substantial changes in snowmelt, evapotranspiration, surface runoff, soil water, and groundwater flow simulations. Thus, any study that is relying on these unmeasured components (e.g., water quality, climate change impacts, and best management practice studies) should choose calibration periods selectively and carefully.

• Drawdown processes of Poyang Lake level during dry season were quickened post the operation of Three Gorges Dam (TGD).
• Antecedent near-term water level fluctuations exerted strong influences on vegetation coverage.
• Quickened drawdown processes of Poyang Lake accelerated vegetation expansion.

Catchment characteristics and sources of stream water affect DOM biodegradability and downstream transport. TOC concentrations and DOM biodegradation rates were highest during low flow when water and DOM mostly originated from bogs and uplands were disconnected from streams. Peatlands, even if only partial areas of catchments, override effects of uplands on the concentrations and biodegradability stream of DOM.

• A two-dimensional hydrodynamic model (MIKE 21) was established to simulate the hydrological process in the marsh wetland.
• The dynamic suitable water levels in Zhalong Wetland was obtained.
• The optimized schemes about the water diversion amount and timing were proposed to improve the compliance rate of the suitable water levels.

Many factors drive urban stream temperature heterogeneity. In this study, wastewater treatment plants were the strongest driver of downstream temperature changes; treatment plants that discharged into larger streams, had cooler effluent, or had lower discharge had less impact. Urban headwater sites with more local riparian canopy had cooler maximum temperatures, while watershed-scale impervious area was associated with greater surge frequency and magnitude during some storms. Restoring riparian canopy in urban settings may impact stream temperatures more than treating impervious area.

Groundwater tracer-tests are combined with 1-year high-frequency data of dissolved oxygen, water temperature, and water-levels, and data-driven simulations to assess the seasonal and event-term variations of transport and consumption of riparian dissolved oxygen and the further implications for redox processes.

Distribution of trend slopes per decade of E_pen, E_rad, and E_aero in the different stations in the HRB (1970–2017).

• Under the influence of irrigation, the annual variation of E_pen in the agricultural, natural, and desert areas was significantly different.
• From 1970 to 1998, the annual trend slope of E_pen in the agricultural area significantly decreased by 39 mm decade⁻¹. After the implementation of water-saving irrigation, the E_pen in the agricultural areas increased by 54 mm decade⁻¹ from 1998 to 2017.
• The main meteorological factors influencing the variation of E_pen in HRB are U₂ and VPD.

• Modelling of glacier-wide air temperature, energy and mass fluxes.
• Development of two-dimensional satellite based energy and mass balance model.
• Validation of the proposed model with AWS data and sensitivity analysis.

Precipitation samples (n=498) were collected in three locations in central Ohio during 2012–2018. Precipitation samples from Columbus, Galena and Mansfield, Ohio are plotted with a precipitation volume weighted local meteoric water line (LMWL) and an unweighted LMWL to describe the data. Extratropical precipitation (hurricane remnant) samples collected as part of this study are plotted with precipitation occurrences. The extratropical precipitation samples fall along LMWLs, showing that the δ2H–δ18O relationship of extratropical precipitation is consistent with all precipitation occurrences.

Soil aggregate stability increased with the increases of soil organic carbon and light fraction organic carbon. Macroaggregates (>0.25mm) in eroded soil increased with the increase of organic carbon. Increase of heavy fraction organic carbon reduced the slaking effects on aggregates disintegration during splash erosion.

During Typhoon Bailu, the δ¹⁸O values of the instantaneous drip water samples exhibited similar characteristics, like the inverted U-shape of typhoon-induced rainfall, outside of the cave, but they had less negative deviation due to the low precipitation amount (approximately 28.8 mm) and larger drip water source reservoir.

Lagoons interspersed in wetlands increase the mean residence time of the flow. The lagoon mean residence time increases as the lagoon depth increases. The lagoon length did not modify the mean residence time. The flow enters the lagoon through its leading edge and flows out through its trailing edge. Dense nearby lagoon vegetation decreases the lagoon mean residence time, i.e. producing short-circuiting and homogenizing the flow at the leading edge of the lagoon.