Catchment Water Balance Research Articles

Estimation of Lake Outflow from the Poorly Gauged Lake Tana (Ethiopia) Using Satellite Remote Sensing Data

Lake Tana is the largest lake in Ethiopia, and its lake outflow is the source of the Blue Nile River that provides vital water resources for many livelihoods and downstream/international stakeholders. Therefore, it is essential to quantify and monitor the water balance of Lake Tana. However, Lake Tana is poorly gauged, with more than 50% of Lake Tana Basin being ungauged from in-situ measurements, making it difficult to quantify the lake inflow from surrounding basins. The lack of in-situ measurements highlights the need for the innovative application of satellite remote sensing. This study explores how freely accessible satellite remote sensing can be used to complement routine weather data to quantify the water balance of Lake Tana and its surrounding catchments. This study particularly investigates whether the outflow from Lake Tana can be estimated with sufficient accuracy as the residual of the lake water balance. Monthly inflow into lake was computed as the total runoff from the surrounding catchments; the runoff was estimated as the residual of the land-based catchment water balance using satellite precipitation improved with an integrated downscaling-calibration procedure, satellite evapotranspiration, and a correction term for changes in land total storage (soil moisture storage and deep percolation). The outflow from Lake Tana was estimated as the residual of lake water balance by combining satellite-based lake precipitation, changes in water storage, and lake inflow with estimated lake evaporation. Evaluation using limited available measurements showed that estimated annual runoff for two gauged subbasins agreed well with measurements, with differences within 4%. The estimated annual outflow from Lake Tana was also close to measured outflow, with a difference of 12%. However, the estimated monthly runoff from catchments and monthly lake outflow were unsatisfactory, with large errors.

Tropical Montane Cloud Forests in the Orinoco River basin: Inferring fog interception from through-fall dynamics

The interaction between vegetation and the atmosphere is highly complex in fog affected ecosystems like Tropical Montane Cloud Forests (TMCFs). Despite acknowledging fog effects on the canopy’s water balance, quantifying their influence remains challenging. While the reduction in potential evaporation that is caused by fog presence, is largely independent of land cover, fog interception itself strongly depends on the land-cover’s vegetation characteristics. A better understanding of how these two fog related processes affect the water balance is highly relevant under current land-use and climate-change pressures. In this study we evaluate the different fog effects on TMCFs’ canopy interception combining model simulations and high temporal resolution (10 min) observations that were collected in different TMCF regeneration stages: early succession, secondary and old-growth TMCFs. We also analyse the difficulties in closing catchment water balances caused by limitations on the interpretation of throughfall data to properly represent these fog effects.Results show that different fog frequencies along elevation affect potential evaporation. The higher elevation old-growth TMCFs have a lower simulated evaporation and a lower dry canopy frequency than the low elevation secondary and early succession forests. Furthermore, we show that fog water inputs during fog-only events, even though higher at the higher elevation, are irrelevant as water inputs (from 0.8% to 1.6% of measured rainfall), but fog’s contribution to through-fall during foggy rainfall events can be more relevant (from 5.8%–12.8% of measured rainfall). Additional to the fog trends along the elevation, we also uncover variable fog-vegetation interactions controlled by differences in canopy water storages as a function of forest cover. Each evaluated process has associated uncertainties, which together cumulatively explain why closing a water budget in TMCF catchments is limited by data collection methods that probably do not capture all relevant fog effects. In addition, this study also indicates that the temporal resolution of measured rainfall and through-fall and compensating effects of canopy parameters that are estimated by the commonly used Rutter canopy-rainfall interception model, pose an additional challenge to understand and quantify fog effects in the water budgets of TMCFs.

Impact of irrigation on the water level of Lake Maybar, Northeast Ethiopia

ABSTRACTThe main objective of the research is to investigate the impact of irrigation water use on the water level of Lake Maybar. The collected data were tested for their consistency using outlier test and then analysed to estimate the components of catchment and lake water balances. Water Balance (WTRBLN) software was used to simulate the observed flow (catchment response) at the outlet of river Kori Sheleko. The model performance was tested using a Nash–Sutcliffe correlation, R2, and showed better agreement (R2 = 94.3%) between observed and predicted flows. The lake water balance at two scenarios of development of irrigation within Maybar Lake Basin was analysed. The result at scenario-1 (existing irrigation development) showed a water level reduction of about 0.76 m, and at scenario-2 (exploitation of all potential irrigation areas) it was 1.49 m. Through this impact study using a Water Balance Model, it was shown that the consumptive water use for irrigation development heavily affected the natural water level of Lake Maybar.

Spatially distributed potential evapotranspiration modeling and climate projections

Evapotranspiration integrates energy and mass transfer between the Earth's surface and atmosphere and is the most active mechanism linking the atmosphere, hydrosphsophere, lithosphere and biosphere. This study focuses on the fine resolution modeling and projection of spatially distributed potential evapotranspiration on the large catchment scale as response to climate change. Six potential evapotranspiration designed algorithms, systematically selected based on a structured criteria and data availability, have been applied and then validated to long-term mean monthly data for the Shannon River catchment with a 50m2 cell size. The best validated algorithm was therefore applied to evaluate the possible effect of future climate change on potential evapotranspiration rates. Spatially distributed potential evapotranspiration projections have been modeled based on climate change projections from multi-GCM ensembles for three future time intervals (2020, 2050 and 2080) using a range of different Representative Concentration Pathways producing four scenarios for each time interval. Finally, seasonal results have been compared to baseline results to evaluate the impact of climate change on the potential evapotranspiration and therefor on the catchment dynamical water balance. The results present evidence that the modeled climate change scenarios would have a significant impact on the future potential evapotranspiration rates. All the simulated scenarios predicted an increase in potential evapotranspiration for each modeled future time interval, which would significantly affect the dynamical catchment water balance. This study addresses the gap in the literature of using GIS-based algorithms to model fine-scale spatially distributed potential evapotranspiration on the large catchment systems based on climatological observations and simulations in different climatological zones. Providing fine-scale potential evapotranspiration data is very crucial to assess the dynamical catchment water balance to setup management scenarios for the water abstractions. This study illustrates a transferable systematic method to design GIS-based algorithms to simulate spatially distributed potential evapotranspiration on the large catchment systems.

Evapotranspiration is resilient in the face of land cover and climate change in a humid temperate catchment

AbstractIn temperate humid catchments, evapotranspiration returns more than half of the annual precipitation to the atmosphere, thereby determining the balance available to recharge groundwaters and support stream flow and lake levels. Changes in evapotranspiration rates and, therefore, catchment hydrology could be driven by changes in land use or climate. Here, we examine the catchment water balance over the past 50 years for a catchment in southwest Michigan covered by cropland, grassland, forest, and wetlands. Over the study period, about 27% of the catchment has been abandoned from row‐crop agriculture to perennial vegetation and about 20% of the catchment has reverted to deciduous forest, and the climate has warmed by 1.14 °C. Despite these changes in land use, the precipitation and stream discharge, and by inference catchment‐scale evapotranspiration, have been stable over the study period. The remarkably stable rates of evapotranspirative water loss from the catchment across a period of significant land cover change suggest that rainfed annual crops and perennial vegetation do not differ greatly in evapotranspiration rates, and this is supported by measurements of evapotranspiration from various vegetation types based on soil water monitoring in the same catchment. Compensating changes in the other meteorological drivers of evaporative water demand besides air temperature—wind speed, atmospheric humidity, and net radiation—are also possible but cannot be evaluated due to insufficient local data across the 50‐year period. Regardless of the explanation, this study shows that the water balance of this landscape has been resilient in the face of both land cover and climate change over the past 50 years.

Impact of climate seasonality on catchment yield: A parameterization for commonly-used water balance formulas

This paper examines the hydrological impact of the seasonality of precipitation and maximum evaporation: seasonality is, after aridity, a second-order determinant of catchment water yield. Based on a data set of 171 French catchments (where aridity ranged between 0.2 and 1.2), we present a parameterization of three commonly-used water balance formulas (namely, Turc-Mezentsev, Tixeront-Fu and Oldekop formulas) to account for seasonality effects. We quantify the improvement of seasonality-based parameterization in terms of the reconstitution of both catchment streamflow and water yield. The significant improvement obtained (reduction of RMSE between 9 and 14% depending on the formula) demonstrates the importance of climate seasonality in the determination of long-term catchment water balance.

Invited perspectives: Hydrological perspectives on precipitation intensity-duration thresholds for landslide initiation: proposing hydro-meteorological thresholds

Abstract. Many shallow landslides and debris flows are precipitation initiated. Therefore, regional landslide hazard assessment is often based on empirically derived precipitation intensity-duration (ID) thresholds and landslide inventories. Generally, two features of precipitation events are plotted and labeled with (shallow) landslide occurrence or non-occurrence. Hereafter, a separation line or zone is drawn, mostly in logarithmic space. The practical background of ID is that often only meteorological information is available when analyzing (non-)occurrence of shallow landslides and, at the same time, it could be that precipitation information is a good proxy for both meteorological trigger and hydrological cause. Although applied in many case studies, this approach suffers from many false positives as well as limited physical process understanding. Some first steps towards a more hydrologically based approach have been proposed in the past, but these efforts received limited follow-up. Therefore, the objective of our paper is to (a) critically analyze the concept of precipitation ID thresholds for shallow landslides and debris flows from a hydro-meteorological point of view and (b) propose a trigger–cause conceptual framework for lumped regional hydro-meteorological hazard assessment based on published examples and associated discussion. We discuss the ID thresholds in relation to return periods of precipitation, soil physics, and slope and catchment water balance. With this paper, we aim to contribute to the development of a stronger conceptual model for regional landslide hazard assessment based on physical process understanding and empirical data.

Hydrological Analysis Using Satellite Remote Sensing Big Data and CREST Model

Hydrological modeling significantly contributes to the understanding of catchment water balance and water resource management and mitigates negative impacts of flooding. Considering the advantages of satellite remote sensing big data and the coupled routing and excess storage (CREST) model, this paper investigates the hydrological modeling in the Shehong basin during 2006–2013. The results show that humid Shehong basin has main rainfalls in summer (From May to September). For the monthly average rainfall and streamflow, there is a remarkable increase (+52%) in discharge and a smaller increase (+18%) in rainfall in the second period (2010–2013) relative to the first period (2006–2009). The CREST model was calibrated using China gauge-based daily precipitation analysis for the period of 2006–2009, followed by a favorable performance with Nash-Sutcliffe coefficient efficiency (NSCE) of 0.77, correlation coefficient (CC) up to 0.88 and −11% Bias. The model validation shows an error metric with NSCE of 0.74, CC of 0.87 and −11.7% Bias. In terms of water balance modeling results at Shehong basin, the runoff and rainfall estimates from CREST model coincide well with the gauge observations, indicating the model captures the appropriate signature of soil moisture variability. Therefore, the satellite-based precipitation product is feasible in hydrological prediction, and the CREST models the interaction between surface and subsurface water flow process in the Shehong basin.

Water Balance Dynamics during Ten Years of Ecological Development at Chicken Creek Catchment

Core Ideas Water balance was calculated for the constructed catchment Chicken Creek. Influence of abiotic and biotic factors feedback mechanisms on the hydrology was determined. Different phases were derived during the development of the ecohydrological system. Difficulties in quantitatively closing the water balance of catchments arise when upscaling point measurements and from insufficient knowledge of the physical boundaries, inner structure, and storage volumes of natural catchments. In addition, there is a strong need for generalizing the relationship between catchment characteristics and hydrological response. Therefore, experimental catchments with well‐known boundaries and conditions could contribute valuable data to hydrological and critical zone research. One of the most well‐established and largest constructed catchments is the Chicken Creek catchment (6 ha including a pond, Brandenburg, Germany) representing an initial ecosystem undergoing highly dynamic ecological development starting from clearly defined starting conditions. Directly after completion of the construction, extensive monitoring equipment was installed to track the ecosystem development and to capture the spatiotemporal variability of meteorological, hydrological, ecological, and soil conditions and vegetation succession. In this study, we focused on the water balance dynamics of the Chicken Creek catchment for the period 2005 to 2015 as influenced by ecological development. Water storage in the catchment was calculated from a three‐dimensional model of groundwater volumes, soil moisture measurements, and water level recordings of the pond. The catchment water balance equation was resolved for evapotranspiration, the only part that was not measured directly. Time series of meteorological, hydrological, and ecological data for 10 yr enabled us to characterize the transient development of the catchment and to evaluate the effect of different feedback mechanisms on catchment hydrology.

Incorporating the Vadose Zone into the Budyko Framework

The Budyko framework provides a quantitative description of long-term average annual evapotranspiration at catchment scales in terms of macro-climatic variables. This framework, however, makes no reference to the vadose zone because it neglects changes in ubsurface storage in the catchment water balance. Recent studies have shown clearly that vadose-zone water storage cannot be neglected at sub-catchment or sub-annual space and time scales, resulting in numerous model attempts to extend the original Budyko framework to incorporate the full water balance equation. Here we apply the approach taken in a companion paper on the original Budyko framework to show that it can be generalized rigorously to include changes in vadose-zone water storage in a manner that is both parsimonious in hypotheses and broad in scope.

Climatic and physiographic controls of spatial variability in surface water balance over the contiguous United States using the Budyko relationship

AbstractThe geographic variability in the partitioning of precipitation into surface runoff (Q) and evapotranspiration (ET) is fundamental to understanding regional water availability. The Budyko equation suggests this partitioning is strictly a function of aridity, yet observed deviations from this relationship for individual watersheds impede using the framework to model surface water balance in ungauged catchments and under future climate and land use scenarios. A set of climatic, physiographic, and vegetation metrics were used to model the spatial variability in the partitioning of precipitation for 211 watersheds across the contiguous United States (CONUS) within Budyko's framework through the free parameter ω. A generalized additive model found that four widely available variables, precipitation seasonality, the ratio of soil water holding capacity to precipitation, topographic slope, and the fraction of precipitation falling as snow, explained 81.2% of the variability in ω. The ω model applied to the Budyko equation explained 97% of the spatial variability in long‐term Q for an independent set of watersheds. The ω model was also applied to estimate the long‐term water balance across the CONUS for both contemporary and mid‐21st century conditions. The modeled partitioning of observed precipitation to Q and ET compared favorably across the CONUS with estimates from more sophisticated land‐surface modeling efforts. For mid‐21st century conditions, the model simulated an increase in the fraction of precipitation used by ET across the CONUS with declines in Q for much of the eastern CONUS and mountainous watersheds across the western United States.

Remote sensing upscaling of interception loss from isolated oaks: Sardon catchment case study, Spain

Tree interception loss from two Mediterranean oak species, Quercus ilex (Q.i.) and Quercus pyrenaica (Q.p.), was estimated during 2-year period (1 October 2011 to 30 September 2013) in sparsely vegetated Sardon catchment (∼80km2, Spain) by: i) rainfall, throughfall and stemflow measurements; ii) Gash model temporal extrapolation; and iii) remote-sensing spatial upscaling. The annual, measured tree interception losses (Im) of Q.i. and Q.p. in the first year were 51% and 16% of P (335mm) and in the second, 46% and 10% of P (672mm), respectively. The revised Gash analytical model of rainfall interception loss, extrapolated well the Im temporal variability of Q.i. and Q.p., provided the throughfall-based, and not Pennman-Monteith-based, average wet canopy evaporation rates were used. Finally, a novel method of spatial upscaling of a tree-based interception loss into plot- and catchment-scale, using per-species, reference tree interception loss and object-attributes derived from satellite imagery, was proposed. The interception losses from Q.i. and Q.p. were upscaled first into two homogeneous plots (1-ha each and both with ∼20% canopy cover), one with Q.i. and the other with Q.p. oaks and then into the entire Sardon catchment with ∼7% canopy cover. The obtained annual-mean, plot interception losses were 9.5% of P in evergreen Q.i. and 2.5% of P in deciduous Q.p. plot. The annual-mean catchment interception loss was 1.4% of P. The proposed upscaling method is expected to improve catchment water balances, replacing common arbitrary or literature based tree interception loss estimates.

A Case Study Examining the Efficacy of Drainage Setbacks for Limiting Effects to Wetlands in the Prairie Pothole Region, USA

Abstract The enhancement of agricultural lands through the use of artificial drainage systems is a common practice throughout the United States, and recently the use of this practice has expanded in the Prairie Pothole Region. Many wetlands are afforded protection from the direct effects of drainage through regulation or legal agreements, and drainage setback distances typically are used to provide a buffer between wetlands and drainage systems. A field study was initiated to assess the potential for subsurface drainage to affect wetland surface-water characteristics through a reduction in precipitation runoff, and to examine the efficacy of current U.S. Department of Agriculture drainage setback distances for limiting these effects. Surface-water levels, along with primary components of the catchment water balance, were monitored over 3 y at four seasonal wetland catchments situated in a high-relief terrain (7–11% slopes). During the second year of the study, subsurface drainage systems were installed in two of the catchments using drainage setbacks, and the drainage discharge volumes were monitored. A catchment water-balance model was used to assess the potential effect of subsurface drainage on wetland hydrology and to assess the efficacy of drainage setbacks for mitigating these effects. Results suggest that overland precipitation runoff can be an important component of the seasonal water balance of Prairie Pothole Region wetlands, accounting on average for 34% (19–49%) or 45% (39–49%) of the annual (includes snowmelt runoff) or seasonal (does not include snowmelt) input volumes, respectively. Seasonal (2014–2015) discharge volumes from the localized drainage systems averaged 81 m3 (31–199 m3), and were small when compared with average combined inputs of 3,745 m3 (1,214–6,993 m3) from snowmelt runoff, direct precipitation, and precipitation runoff. Model simulations of reduced precipitation runoff volumes as a result of subsurface drainage systems showed that ponded wetland surface areas were reduced by an average of 590 m2 (141–1,787 m2), or 24% (3–46%), when no setbacks were used (drainage systems located directly adjacent to wetland). Likewise, wetland surface areas were reduced by an average of 141 m2 (23–464 m2), or 7% (1–28%), when drainage setbacks (buffer) were used. In totality, the field data and model simulations suggest that the drainage setbacks should reduce, but not eliminate, impacts to the water balance of the four wetlands monitored in this study that were located in a high-relief terrain. However, further study is required to assess the validity of these conclusions outside of the limited parameters (e.g., terrain, weather, soils) of this study and to examine potential ecological effects of altered wetland hydrology.

Sensitivity of potential evapotranspiration to changes in climate variables for different Australian climatic zones

Abstract. Assessing the factors that have an impact on potential evapotranspiration (PET) sensitivity to changes in different climate variables is critical to understanding the possible implications of climatic changes on the catchment water balance. Using a global sensitivity analysis, this study assessed the implications of baseline climate conditions on the sensitivity of PET to a large range of plausible changes in temperature (T), relative humidity (RH), solar radiation (Rs) and wind speed (uz). The analysis was conducted at 30 Australian locations representing different climatic zones, using the Penman–Monteith and Priestley–Taylor PET models. Results from both models suggest that the baseline climate can have a substantial impact on overall PET sensitivity. In particular, approximately 2-fold greater changes in PET were observed in cool-climate energy-limited locations compared to other locations in Australia, indicating the potential for elevated water loss as a result of increasing actual evapotranspiration (AET) in these locations. The two PET models consistently indicated temperature to be the most important variable for PET, but showed large differences in the relative importance of the remaining climate variables. In particular for the Penman–Monteith model, wind and relative humidity were the second-most important variables for dry and humid catchments, respectively, whereas for the Priestley–Taylor model solar radiation was the second-most important variable, with the greatest influence in warmer catchments. This information can be useful to inform the selection of suitable PET models to estimate future PET for different climate conditions, providing evidence on both the structural plausibility and input uncertainty for the alternative models.

A site-level comparison of lysimeter and eddy covariance flux measurements of evapotranspiration

Abstract. Accurate measurements of evapotranspiration are required for many meteorological, climatological, ecological, and hydrological research applications and developments. Here we examine and compare two well-established methods to determine evapotranspiration at the site level: lysimeter-based measurements (EL) and eddy covariance (EC) flux measurements (EEC). The analyses are based on parallel measurements carried out with these two methods at the research catchment Rietholzbach in northeastern Switzerland, and cover the time period of June 2009 to December 2015. The measurements are compared on various timescales, and with respect to a 40-year lysimeter-based evapotranspiration time series. Overall, the lysimeter and EC measurements agree well, especially on the annual timescale. On that timescale, the long-term lysimeter measurements also correspond well with catchment water-balance estimates of evapotranspiration. This highlights the representativeness of the site-level lysimeter and EC measurements for the entire catchment despite their comparatively small source areas and the heterogeneous land use and topography within the catchment. Furthermore, we identify that lack of reliable EC measurements using open-path gas analyzers during and following precipitation events (due to limitations of the measurement technique under these conditions) significantly contributes to an underestimation of EEC and to the overall energy balance gap at the site.

Vegetation dynamics and climate seasonality jointly control the interannual catchment water balance in the Loess Plateau under the Budyko framework

Abstract. Within the Budyko framework, the controlling parameter (ω in the Fu equation) is widely considered to represent landscape conditions in terms of vegetation coverage (M); however, some qualitative studies have concluded that climate seasonality (S) should be incorporated in ω. Here, we discuss the relationship between ω, M, and S, and further develop an empirical equation so that the contributions from M to actual annual evapotranspiration (ET) can be determined more accurately. Taking 13 catchments in the Loess Plateau as examples, ω was found to be well correlated with M and S. The developed empirical formula for ω calculations at the annual scale performed well for estimating ET by the cross-validation approach. By combining the Budyko framework with the semi-empirical formula, the contributions of changes in ω to ET variations were further decomposed as those of M and S. Results showed that the contributions of S to ET changes ranged from 0.1 to 74.8 % (absolute values). Therefore, the impacts of climate seasonality on ET cannot be ignored, otherwise the contribution of M to ET changes will be estimated with a large error. The developed empirical formula between ω, M, and S provides an effective method to separate the contributions of M and S to ET changes.

Spatial Interpolation of Daily Precipitation in a High Mountainous Watershed Based on Gauge Observations and a Regional Climate Model Simulation

Abstract Precipitation is a primary climate forcing factor in catchment hydrology, and its spatial distribution is essential for understanding the spatial variability of ecohydrological processes in a catchment. In mountainous areas, meteorological stations are generally too sparse to represent the spatial distribution of precipitation. This study develops a spatial interpolation method that combines meteorological observations and regional climate model (RCM) outputs. The method considers the precipitation–elevation relationship in the mountain region and the topographic effects, especially the mountain blocking effect. Furthermore, using this method, this study produced a 3-km-resolution precipitation dataset from 1960 to 2014 in the middle and upper reaches of the Heihe River basin located on the northern slope of the Qilian Mountains in the northeastern Tibetan Plateau. Cross validation based on the station observations showed that this method is reasonable. The rationality of the interpolated precipitation data was also evaluated by the catchment water balances using the observed river discharge and the actual evapotranspiration based on remote sensing. The interpolated precipitation data were compared with the China Gauge-Based Daily Precipitation Analysis product and the RCM output and was shown to be optimal. The results showed that the proposed method effectively used the information from the meteorological observations and the RCM simulations and provided the spatial distributions of daily precipitations with reasonable accuracy and high resolution, which is important for a distributed hydrological simulation at the catchment scale.

Estimation of the climate change impact on a catchment water balance using an ensemble of GCMs

This work evaluates the impact of climate change on the water balance of a catchment in India. Rainfall and hydro-meteorological variables for current (20C3M scenario, 1981–2000) and two future time periods: mid of the 21st century (2046–2065) and end of the century (2081–2100) are simulated using Modified Markov Model-Kernel Density Estimation (MMM-KDE) and k-nearest neighbor downscaling models. Climate projections from an ensemble of 5 GCMs (MPI-ECHAM5, BCCR-BCM2.0, CSIRO-mk3.5, IPSL-CM4, and MRI-CGCM2) are used in this study. Hydrologic simulations for the current as well as future climate scenarios are carried out using Soil and Water Assessment Tool (SWAT) integrated with ArcGIS (ArcSWAT v.2009). The results show marginal reduction in runoff ratio, annual streamflow and groundwater recharge towards the end of the century. Increased temperature and evapotranspiration project an increase in the irrigation demand towards the end of the century. Rainfall projections for the future shows marginal increase in the annual average rainfall. Short and moderate wet spells are projected to decrease, whereas short and moderate dry spells are projected to increase in the future. Projected reduction in streamflow and groundwater recharge along with the increase in irrigation demand is likely to aggravate the water stress in the region under the future scenario.

The Transferability of Terrestrial Water Balance Components under Uncertainty and Nonstationarity: A Case Study of the Coastal Plain Watershed in the Southeastern USA

AbstractsThe challenges posed by nonstationarity in predicting catchment water balance components motivated this study to test the stationary versus nonstationarity hypothesis and detect changes in the watershed response to land use land cover (LULC) alterations, and climate variability and change. The focus is on a two‐step procedure that includes model calibration of Soil and Water Assessment Tool using a sequential Bayesian uncertainty algorithm (i.e. sequential uncertainty fitting), followed by nonstationary assessment of water balance component using extreme value analysis over an Atlantic coastal plain watershed in the southeastern USA. Analysis suggests that the uncertainty of Soil and Water Assessment Tool model is statistically aligned with LULC alterations that increased the sensitivity of Manning's roughness coefficient, transmission loss and the resistance of the soil matrix to water flow. Changes in LULC along with variability in the magnitude, timing and frequency of precipitation diminished surface runoff and groundwater contribution to the river system whereas it increased evapotranspiration with a substantial decline in water storage capacity. Nonstationary assessment of water balance using extreme value analysis model further revealed a functional form of stationary behaviour (no trends) prior to LULC alteration while large amplification was detected during post‐changes. The results and findings presented in this paper confirm our hypothesis about a combined effect of climate and LULC changes on hydrological functions and that variation of these fingerprints elucidates the presence of nonstationarity in the watershed system. Copyright © 2017 John Wiley & Sons, Ltd.

The impacts of a changing climate on catchment water balance and forest management

AbstractClimate change has serious impacts on forest services with regard to the spatial and temporal distribution of water within catchments. Hence, combined forest and catchment management in a changing climate is a crucial concern for people and society. To assess hydrological processes and water resources in two forested headwater catchments in south‐west Germany the physical based hydrological model ArcAPEX was calibrated to investigate climate change scenarios for the near (2021–2050) and far (2071–2100) future. Even though the trend in temperature is positive in most regional climate change scenarios for south‐west Germany, the precipitation trend is quite ambiguous. Different precipitation scenarios give access to the possible bandwidth between water stress and flood generation. Our results can be used to describe water resources and discharge characteristics under conditions of different land use change scenarios.Management option for a sustainable forestry and flood mitigation will be to “spread the risk” by creating forests with a high biodiversity and a prioritization of forest services and functions. The principle is to find “no‐regret” decisions. In this sense, final decisions should not be taken too early, and several options should be kept open, such as dealing with increasingly frequent droughts on one hand and increased runoff generation on the other hand. Thus, it should remain possible for forest and catchment management authorities to react to possible developments in an uncertain future.