Case Study Of Catchment Research Articles

Can current management maintain forest landscape multifunctionality in the Eastern Alps in Austria under climate change?

In Central Europe, management of forests for multiple ecosystem services (ES) has a long tradition and is currently drawing much attention due to increasing interest in non-timber services. In face of a changing climate and diverse ES portfolios, a key issue for forest managers is to assess vulnerability of ES provisioning. In a case study catchment of 250 ha in the Eastern Alps, the currently practiced uneven-aged management regime (BAU; business as usual) which is based on irregularly shaped patch cuts along skyline corridors was analysed under historic climate (represented by the period 1961–1990) and five transient climate change scenarios (period 2010–2110) and compared to an unmanaged scenario (NOM). The study addressed (1) the future provisioning of timber, carbon sequestration, protection against gravitational hazards, and nature conservation values under BAU management, (2) the effect of spatial scale (1, 5, 10 ha grain size) in mapping ES indicators and (3) how the spatial scale of ES assessment affects the simultaneous provision of several ES (i.e. multifunctionality). The analysis employed the PICUS forest simulation model in combination with novel landscape assessment tools. In BAU management, timber harvests were smaller than periodic increments. The resulting increase in standing stock benefitted carbon sequestration. In four out of five climate change scenarios, volume increment was increasing. With the exception of the mildest climate change scenario (+2.6 °C, no change in precipitation), all other analysed climate change scenarios reduced standing tree volume, carbon pools and number of large old trees, and increased standing deadwood volume due to an intensifying bark beetle disturbance regime. However, increases in deadwood and patchy canopy openings benefitted bird habitat quality. Under historic climate, the NOM regime showed better performance in all non-timber ES. Under climate change conditions, the damages from bark beetle disturbances increased more in NOM compared with BAU. Despite favourable temperature conditions in climate change scenarios, the share of admixed broadleaved species was not increasing in BAU management, mainly due to the heavy browsing pressure by ungulates. In NOM, it even decreased and mean tree age increased. Thus, in the long run NOM may enter a phase of lower resilience compared with BAU. Most ES indicators were fairly insensitive to the spatial scale of indicator mapping. ES indicators that were based on sparse tree and stand attributes such as rare admixed tree species, large snags and live trees achieved better results when mapped at larger scales. The share of landscape area with simultaneous provisioning of ES at reasonable performance levels (i.e. multifunctionality) decreased with increasing number of considered ES, while it increased with increasing spatial scale of the assessment. In the case study, landscape between 53 and 100 % was classified as multifunctional, depending on number and combinations of ES.

Exploration of optimal time steps for daily precipitation bias correction: a case study using a single grid of RCM on the River Exe in southwest England

ABSTRACTBias correction is a necessary post-processing procedure in order to use regional climate model (RCM)-simulated local climate variables as the input data for hydrological models due to systematic errors of RCMs. Most of the present bias-correction methods adjust statistical properties between observed and simulated data based on a predefined duration (e.g. a month or a season). However, there is a lack of analysis of the optimal period for bias correction. This study attempted to address the question whether there is an optimal number for bias-correction groups (i.e. optimal bias-correction period). To explore this we used a catchment in southwest England with the regional climate model HadRM3 precipitation data. The proposed methodology used only one grid of RCM in the Exe catchment, one emissions scenario (A1B) and one member (Q0) among 11 members of HadRM3. We tried 13 different bias-correction periods from 3-day to 360-day (i.e. the whole of one year) correction using the quantile mapping method. After the bias correction a low pass filter was used to remove the high frequencies (i.e. noise) followed by estimating Akaike’s information criterion. For the case study catchment with the regional climate model HadRM3 precipitation, the results showed that a bias-correction period of about 8 days is the best. We hope this preliminary study on the optimum number bias-correction period for daily RCM precipitation will stimulate more research to improve the methodology with different climatic conditions. Future efforts on several unsolved problems have been suggested, such as how strong the filter should be and the impact of the number of bias correction groups on river flow simulations.Editor M.C. Acreman Associate editor S. Kanae

Can water sensitive urban design systems help to preserve natural channel-forming flow regimes in an urbanised catchment?

Increased stormwater runoff and pollutant loads due to catchment urbanisation bring inevitable impacts on the physical and ecological conditions of environmentally sensitive urban streams. Water sensitive urban design (WSUD) has been recognised as a possible means to minimise these negative impacts. This paper reports on a study that investigated the ability of infiltration-based WSUD systems to replicate the predevelopment channel-forming flow (CFF) regime in urban catchments. Catchment models were developed for the 'pre-urban', 'urban' and 'managed' conditions of a case study catchment and the hydrological effect on CFF regime was investigated using a number of flow indices. The results clearly show that changes to flow regime are apparent under urban catchment conditions and are even more severe under highly urbanised conditions. The use of WSUD systems was found to result in the replication of predevelopment flow regimes, particularly at low levels of urbanisation. Under highly urbanised conditions (of managed catchments) overcontrol of the CFF indices was observed as indicated by flow statistics below their pre-urban values. The overall results suggest that WSUD systems are highly effective in replicating the predevelopment CFF regime in urban streams and could be used as a means to protect environmentally sensitive urban streams.

Environmental implications of using ‘underutilised agricultural land’ for future bioenergy crop production

Land use change effects have emerged as an important area of global bioenergy sustainability policy and research. ‘Underutilised agricultural land’ has been previously proposed as a potential option for future bioenergy feedstock production that may minimise the environmental and social challenges of land use change. However, this has not been well tested to date. Our research aims to evaluate whether conversion of these lands to selected bioenergy crops can lead to favourable environmental outcomes for eight indicators related to water quantity and quality, and terrestrial biodiversity. A spatially explicit evaluation framework based on GIS was developed to quantify the environmental effects of land use change. The land use change scenarios, established in a case study region in subtropical Queensland, Australia, were for the production of Pongamia and two native eucalypt species (Spotted gum and Chinchilla white gum) on (i) existing ‘underutilised’ open grazing areas, (ii) existing ‘underutilised’ forested grazing areas, and (iii) all available ‘underutilised agricultural land’ in the case study catchment, under both low and high management intensity. We found that environmental benefits can be gained in scenarios where (i) open grazing areas (e.g., pastures) were used; (ii) native woody perennial bioenergy crops were planted; and (iii) the new plantations were under low management intensity. Other scenarios resulted in reduced environmental outcomes. The results flagged the importance of careful planning and management strategies, and the need for future bioenergy policy to provide more detailed prescriptions concerning land use planning and management if ‘underutilised agricultural lands’ are used for future bioenergy crop production.

Micro-level crafting of institutions within integrated catchment management: Early lessons of adaptive governance from a catchment-based approach case study in England

There has been considerable interest and discussion surrounding institutional design and governance in the areas of planning, political studies and policy development and more recently natural resource management. Within England, like much of Europe, an integrated catchment management, called the catchment-based approach (CaBA), has been developed when implementing the European Union (EU) Water Framework Directive (WFD). This is seen as both a driver for stricter standards for water quality and ecological status in water course and encouraging the active involvement of stakeholders and communities in both planning and action. This paper analyses institutional design at the local level from the perspective of two concepts, namely institutional governance and social–ecological systems. The intension is to highlight synergies between the two concepts. Through this a new aspect of institutional design is revealed, the micro-level or ‘crafting’ of institutions by local actors. The paper identifies criteria that are associated with this aspect and analyses an integrated catchment case study in England. The paper concludes that the current policy approach in England, and potentially elsewhere in Europe, offers potential for the ‘crafting’ of institutions and at the local social–ecological systems scale this has potential for positive benefits such as great understanding and locally effective governance. Both would assist in achieving policy objectives, such as those of the WFD. The case study utilised an effective participatory approach that was, according to the criteria, robust and transferable in developing an adaptive governance approach.

A cloud based tool for knowledge exchange on local scale flood risk

There is an emerging and urgent need for new approaches for the management of environmental challenges such as flood hazard in the broad context of sustainability. This requires a new way of working which bridges disciplines and organisations, and that breaks down science-culture boundaries. With this, there is growing recognition that the appropriate involvement of local communities in catchment management decisions can result in multiple benefits. However, new tools are required to connect organisations and communities. The growth of cloud based technologies offers a novel way to facilitate this process of exchange of information in environmental science and management; however, stakeholders need to be engaged with as part of the development process from the beginning rather than being presented with a final product at the end.Here we present the development of a pilot Local Environmental Virtual Observatory Flooding Tool. The aim was to develop a cloud based learning platform for stakeholders, bringing together fragmented data, models and visualisation tools that will enable these stakeholders to make scientifically informed environmental management decisions at the local scale. It has been developed by engaging with different stakeholder groups in three catchment case studies in the UK and a panel of national experts in relevant topic areas. However, these case study catchments are typical of many northern latitude catchments. The tool was designed to communicate flood risk in locally impacted communities whilst engaging with landowners/farmers about the risk of runoff from the farmed landscape. It has been developed iteratively to reflect the needs, interests and capabilities of a wide range of stakeholders. The pilot tool combines cloud based services, local catchment datasets, a hydrological model and bespoke visualisation tools to explore real time hydrometric data and the impact of flood risk caused by future land use changes. The novel aspects of the pilot tool are; the co-evolution of tools on a cloud based platform with stakeholders, policy and scientists; encouraging different science disciplines to work together; a wealth of information that is accessible and understandable to a range of stakeholders; and provides a framework for how to approach the development of such a cloud based tool in the future. Above all, stakeholders saw the tool and the potential of cloud technologies as an effective means to taking a whole systems approach to solving environmental issues. This sense of community ownership is essential in order to facilitate future appropriate and acceptable land use management decisions to be co-developed by local catchment communities. The development processes and the resulting pilot tool could be applied to local catchments globally to facilitate bottom up catchment management approaches.

Changes in runoff regime. The Lomnice catchment case study

Water distribution in landscape is essentially influenced by the nature of the catchment rainfall-runoff process. Firstly, this paper presents an analysis of trends in the rainfall-runoff regime of the Lomnice river basin (South Bohemia, Czech Republic), using a single and double mass curve method. Secondly, the analysis of the rainfall-runoff regime is supplemented by an analysis of the evolution of temperature and snow conditions. Finally, a water balance analysis is performed for three selected years, using the Bilan hydrological model. The aim of the present paper was to find out (1) whether any changes have occurred in the trend of the rainfall-runoff regime of the catchment since 1970, and (2) to what extent these changes may have been caused by anthropogenic activities in the catchment. The results show several changes in the runoff scheme that are not related to the amount of precipitation. This statement follows from the comparison of single mass curves of precipitation and discharges. A comparison of the hydrological balance data for the Lomnice river basin, and the Otava and the Upper Vltava (a higher order stream) river basins led to the following conclusions: (1) There has been a change in the trend of the Lomnice river runoff regime. (2) The runoff regime of the Lomnice river basin differs from the regime of the higher order river basin (the Otava, the Upper Vltava). (3) The changes in the runoff regime in the Lomnice river basin were probably caused mainly by anthropogenic activities, the influence of which disappears within the larger basin (a higher order catchment area). Therefore, when planning sustainable water resources management, it is necessary to consider the impact of human activities not only globally, but also at the local scale.

Can we model the implementation of water sensitive urban design in evolving cities?

This study showcases the dynamic simulation capabilities of the Urban Biophysical Environments And Technologies Simulator (UrbanBEATS) on a Melbourne catchment. UrbanBEATS simulates the planning, design and implementation of water sensitive urban design (WSUD) infrastructure in urban environments. It considers explicitly the interaction between urban and water infrastructure planning through time. The model generates a large number of realizations of different WSUD interventions and their evolution through time based on a user-defined scenario. UrbanBEATS' dynamics was tested for the first time on a historical case study of Scotchman's Creek catchment and was trained using historical data (e.g. planning documents, narratives, urban development and societal information) to adequately reproduce patterns of uptake of specific WSUD technologies. The trained model was also used to explore the implications of more stringent future water management objectives. Results highlighted the challenges of meeting this legislation and the opportunities that can be created through the mix of multiple spatial scales.

Ecosystem services in urban water investment

Increasingly, water agencies and utilities have an obligation to consider the broad environmental impacts associated with investments. To aid in understanding water cycle interdependencies when making urban water supply investment decisions, an ecosystem services typology was augmented with the concept of integrated water resources management. This framework is applied to stormwater harvesting in a case study catchment in Adelaide, South Australia. Results show that this methodological framework can effectively facilitate systematic consideration and quantitative assessment of broad environmental impacts of water supply investments. Five ecosystem service impacts were quantified including provision of 1) urban recreational amenity, 2) regulation of coastal water quality, 3) salinity, 4) greenhouse gas emissions, and 5) support of estuarine habitats. This study shows that ignoring broad environmental impacts can underestimate ecosystem service benefits of water supply investments by a value of up to A$1.36/kL, or three times the cost of operating and maintenance of stormwater harvesting. Rigorous assessment of the public welfare impacts of water infrastructure investments is required to guide long-term optimal water supply investment decisions. Numerous challenges remain in the quantification of broad environmental impacts of a water supply investment including a lack of peer-reviewed studies of environmental impacts, aggregation of incommensurable impacts, potential for double-counting errors, uncertainties in available impact estimates, and how to determine the most suitable quantification technique.

Water cycle modelling of peri-urban hydroecological systems: a case study of the South Creek catchment, Australia

Modelling offers a time efficient and cost-effective approach to integrate and analyse different components of complex peri-urban hydroecological systems. This paper evaluates and applies a catchment water balance model (Peri-Urban SimHyd) developed to simulate the complete water cycle of the South Creek catchment, a complex peri-urban catchment in Western Sydney (Australia). Peri-Urban SimHyd combined the modelling of daily rainfall-runoff from both impervious and pervious surfaces with the modelling of monthly reticulated potable water supply, wastewater flows, and surface and groundwater extractions, to simulate the monthly water balance of the catchment. The model was successful (the Nash-Sutcliffe efficiency >0.68) in simulating the monthly total wastewater discharges and streamflows in the South Creek and its main tributary, the Eastern Creek, over a period of 15 years (1992–2006). The model performance was found to be suitable for simulating macro water balance and catchment yield but not for low streamflow hydrographs. Further, the model demonstrated its applicability in assessing the impacts of water cycle management strategies, i.e. ‘replacement flows’ and ‘water smart farms’ scenarios, on monthly and annual streamflows in the South Creek catchment. In general, Peri-Urban SimHyd has a generic structure and can be employed to assess impacts of various ‘what if’ scenarios on water cycle and streamflows in other peri-urban hydroecological systems.

The history and assessment of effectiveness of soil erosion control measures deployed in Russia

Research activities aimed at design and application of soil conservation measures for reduction of soil losses from cultivated fields started in Russia in the last quarter of the 19th century. A network of "zonal agrofor-estry melioration experimental stations" was organized in the different landscape zones of Russia in the first half of the 20th century. The main task of the experiments was to develop effective soil conservation measures for Russian climatic,soil and land use conditions. The most widespread and large-scale introduction of coun-termeasures to cope with soil erosion by water and wind into agricultural practice supported by serious governmental investments took place during the Soviet Union period after the Second World War. After the Soviet Union collapse in 1991 ,general deterioration of the agricultural economy sector and the absence of investments resulted in cessation of organized soil conservation measures application at the nation-wide level. However, some of the long-term erosion control measures such as forest shelter belts, artificial slope terracing, water diversion dams above formerly active gully heads survived until the present. In the case study of sediment redistribution within the small cultivated catchment presented in this paper an attempt was made to evaluate average annual erosion rates on arable slopes with and without soil conservation measures for two time intervals. It has been found that application of conservation measures on cultivated slopes within the experimental part of the case study catchment has led to a decrease of average soil loss rates by at least 2. 5 2. 8 times. The figures obtained are in good agreement with previously published results of direct monitoring of snowmelt erosion rates, reporting approximately a 3 -fold decrease of average snowmelt erosion rates in the experimental sub-catchment compared to a traditionally cultivated control sub-catchment. A substantial decrease of soil erosion rates on arable slopes has been equally reflected in a corresponding decrease of aggradation rates in the main valley bottom and tributaries.

Sensitivity and uncertainty analysis of mesoscale model downscaled hydro-meteorological variables for discharge prediction

Precipitation and Reference Evapotranspiration (ETo) are the most important variables for rainfall–runoff modelling. However, it is not always possible to get access to them from ground-based measurements, particularly in ungauged catchments. This study explores the performance of rainfall and ETo data from the global European Centre for Medium Range Weather Forecasts (ECMWF) ERA interim reanalysis data for the discharge prediction. The Weather Research and Forecasting (WRF) mesoscale model coupled with the NOAH Land Surface Model is used for the retrieval of hydro-meteorological variables by downscaling ECMWF datasets. The conceptual Probability Distribution Model (PDM) is chosen for this study for the discharge prediction. The input data and model parameter sensitivity analysis and uncertainty estimations are taken into account for the PDM calibration and prediction in the case study catchment in England following the Generalized Likelihood Uncertainty Estimation approach. The goodness of calibration and prediction uncertainty is judged on the basis of the p-factor (observations bracketed by the prediction uncertainty) and the r-factor (achievement of small uncertainty band). The overall analysis suggests that the uncertainty estimates using WRF downscaled ETo have slightly smaller p and r values (p= 0.65; r= 0.58) as compared to ground-based observation datasets (p= 0.71; r= 0.65) during the validation and hence promising for discharge prediction. On the contrary, WRF precipitation has the worst performance, and further research is needed for its improvement (p= 0.04; r= 0.10). Copyright © 2013 John Wiley & Sons, Ltd.

Development and assessment of a daily time-step continuous simulation modelling approach for design flood estimation at ungauged locations: ACRU model and Thukela Catchment case study

The estimation of design floods is necessary for the design of hydraulic structures. Commonly used event-based approaches to design flood estimation have several limitations, which include the estimation of antecedent soil moisture conditions and the assumption that the exceedance probability of the design flood is the same as the exceedance probability of the design rainfall. Many of the limitations of event-based approaches may be overcome by the use of continuous simulation modelling for design flood estimation. This paper contains a brief summary on the development and assessment of a continuous simulationmodelling system for design flood estimation in ungauged catchments. These developments include an investigation into the appropriate spatial scale of model configuration for optimum performance of the system, the temporal disaggregation of daily rainfall for hydrograph generation, flood routing in ungauged catchments and the use of radar information and rain-gauge data to improve the estimation of catchment rainfall. Results from the application of the system for design flood estimation in the Thukela Catchment in South Africa are presented and discussed. The results from the study highlight the challenges of hydrological modelling in an operational catchment and the need for reliable rainfall and runoff data. From the results obtained, it is concluded that reasonable and consistent estimates of design floods in the Thukela Catchment, particularly in smaller sub-catchments, can be obtained using the ACRU model.Keywords: Design flood estimation; continuous simulation modelling, Thukela Catchment

Rainfall -Runoff Modelling using Multi Layer Perceptron Technique - A Case Study of the Upper Kharun Catchment in Chhattisgarh

Modelling rainfall-runoff transformation is essential for several hydrological and water management studies. A rainfall-runoff model was developed for the Upper Kharun catchment (2511 km2) in Chhatisgarh state, based on

Estimating catchment-scale annual soil loss in managed native eucalypt forests, Australia

Conservation of soil and water resources is one of the key criteria underpinning sustainable forest management. While soil and water resources are important determinants of forest productivity, without appropriate assessment of soil erosion risk and the application of best management practices (BMPs), some forest management activities can adversely affect hillslope erosion rates with detrimental consequences for aquatic environments and downstream water users. In the multiple-use native eucalypt forests of New South Wales (NSW), Australia, hazard matrix tables are currently used to identify soil erosion risk based upon rainfall erosivity, soil regolith stability and slope classes at the compartment scale prior to undertaking forestry activities. Resultant “inherent hazard levels” (IHLs) direct the BMPs to be used, such as riparian buffer widths, during harvesting and roading operations. The IHL model, being an ordinal classification system, only provides a relative indication of erosion potential without any quantitative estimate of possible post-harvest erosion rates. To potentially better identify erosion risk and quantify likely soil erosion under a range of forest management and climatic scenarios at the hillslope and/or catchment scale, in this paper we utilised an alternative approach by modelling soil erosion using the empirically-derived Revised Universal Soil Loss Equation in combination with a GIS-based spatially distributed raster analysis. In four case study catchments in Kangaroo River State forest, two of which were subjected to single-tree selection harvesting operations, mean annual changes in soil loss were estimated at a grid cell level. Potential differences in soil loss estimates were assessed before, during and after selective logging. Vegetation cover and soil samples were recorded in a 500×1000m rectangular network laid out across the catchments. Slope gradient was found to contribute substantially to the spatial variability of soil loss estimation across the catchments. However, between-year differences demonstrate that the highest estimated annual rates of soil loss occurred on steep hillslopes when high levels of rainfall were recorded, while the values on those same areas remained considerably lower during low rainfall periods. The major effect of the rainfall component in generating soil erosion overshadows the modest impacts of selective logging operations.

Sobol′’s sensitivity analysis for a distributed hydrological model of Yichun River Basin, China

Summary This paper aims to provide an enhanced understanding of the parameter sensitivities of the Soil and Water Assessment Tool (SWAT) using a variance-based global sensitivity analysis, i.e., Sobol′’s method. The Yichun River Basin, China, is used as a case study, and the sensitivity of the SWAT parameters is analyzed under typical dry, normal and wet years, respectively. To reduce the number of model parameters, some spatial model parameters are grouped in terms of data availability and multipliers are then applied to parameter groups, reflecting spatial variation in the distributed SWAT model. The SWAT model performance is represented using two statistical metrics – Root Mean Square Error (RMSE) and Nash–Sutcliffe Efficiency (NSE) and two hydrological metrics – RunOff Coefficient Error (ROCE) and Slope of the Flow Duration Curve Error (SFDCE). The analysis reveals the individual effects of each parameter and its interactions with other parameters. Parameter interactions contribute to a significant portion of the variation in all metrics considered under moderate and wet years. In particular, the variation in the two hydrological metrics is dominated by the interactions, illustrating the necessity of choosing a global sensitivity analysis method that is able to consider interactions in the SWAT model identification process. In the dry year, however, the individual effects control the variation in the other three metrics except SFDCE. Further, the two statistical metrics fail to identify the SWAT parameters that control the flashiness (i.e., variability of mid-flows) and overall water balance. Overall, the results obtained from the global sensitivity analysis provide an in-depth understanding of the underlying hydrological processes under different metrics and climatic conditions in the case study catchment.

A GIS-based methodology for selecting stormwater disconnection opportunities

The purpose of this paper is to introduce a geographic information system (GIS)-based decision support tool that assists the user to select not only areas where (retrofit) sustainable drainage systems (SuDS) could be implemented within a large catchment (>100 ha), but also to allow discrimination between suitable SuDS techniques based on their likely feasibility and effectiveness. The tool is applied to a case study catchment within London, UK, with the aim of increasing receiving water quality by reducing combined sewer overflow (CSO) spill frequency and volume. The key benefit of the tool presented is to allow rapid assessment of the retrofit SuDS potential of large catchments. It is not intended to replace detailed site investigations, but may help to direct attention to sites that have the greatest potential for retrofit SuDS implementation. Preliminary InfoWorks CS modelling of 'global disconnections' within the case study catchment, e.g. the removal of 50% of the total impervious area, showed that CSO spill volume could be reduced by 55 to 78% during a typical year. Using the disconnection hierarchy developed by the authors, the feasibility of retrofit SuDS deployment within the case study catchment is assessed, and the implications discussed.

Frequency analysis of river water quality using integrated urban wastewater models

In recent years integrated models have been developed to simulate the entire urban wastewater system, including urban drainage systems, wastewater treatment plants, and receiving waterbodies. This paper uses such an integrated urban wastewater model to analyze the frequency of receiving water quality in an urban wastewater system with the aim of assessing the overall system performance during rainfall events. The receiving water quality is represented by two indicators: event mean dissolved oxygen (DO) concentration and event mean ammonium concentration. The compliance probability of the water quality indicators satisfying a specific threshold is used to represent the system performance, and is derived using the rainfall events from a series of 10 years' rainfall data. A strong correlation between the depth of each rainfall event and the associated volume of combined sewer overflow (CSO) discharges is revealed for the case study catchment, while there is a low correlation between the intensity/duration of the rainfall event and the volume of the CSO discharges. The frequency analysis results obtained suggest that the event mean DO and ammonium concentrations have very different characteristics in terms of compliance probabilities at two discharging points for CSO and wastewater treatment plant effluent, respectively. In general, the simulation results provide an understanding of the performance of the integrated urban wastewater system and can provide useful information to support water quality management.

Did tillage erosion play a role in millennial scale landscape development?

ABSTRACTLandscape evolution models (LEMs) quantitatively simulate processes of sedimentation and erosion on millennial timescales. An important aspect of human impact on erosion is sediment redistribution due to agriculture, referred to herein as tillage erosion. In this study we aim to analyse the potential contribution of tillage erosion to landscape development using LEM LAPSUS. The model is calibrated separately for a water erosion process (i) without tillage and (ii) with tillage. The model is applied to the ~250 km2 Torrealvilla case study catchment, SE Spain. We were able to simulate alternating sequences of incision and aggradation, that are important on longer (millennial) timescales. Generally, model results show that tillage erosion adds to deposition in the lower floodplain area, but neither water erosion alone nor water with tillage erosion together could exactly reproduce the observed amounts of erosion and sedimentation for the case study area. In addition, scale effects are apparent. On hillslopes, tillage may contribute importantly to erosion and may fill local depressions. If assessed on the catchment scale, sediments from tillage erosion eventually reach the lower floodplain area where they contribute to deposition. However, water erosion was observed in the model simulations to be the most important process on the catchment scale. This is the first time that tillage erosion has been explicitly included in a landscape evolution model at a millennial timescale and large catchment scale. Copyright © 2012 John Wiley & Sons, Ltd.

Do time‐variable tracers aid the evaluation of hydrological model structure? A multimodel approach

In this paper we explore the use of time‐variable tracer data as a complementary tool for model structure evaluation. We augment the modular rainfall‐runoff modeling framework FUSE (Framework for Understanding Structural Errors) with the ability to track the age distribution of water in all model stores and fluxes. We therefore gain the novel ability to compare tracer/water age signatures measured in a catchment with those predicted using hydrological models built from components based on four existing popular models. Key modeling decisions available in FUSE are evaluated against streamflow tracer dynamics using weekly observations of tracer concentration which reflect the tracer transit time distribution (TTD). Model structure choice is shown to have a significant effect on simulated water age characteristics, even when simulated flow series are very similar. We show that for a Scottish case study catchment, careful selection of model structure enables good predictions of both streamflow and tracer dynamics. We then use FUSE as a hypothesis testing tool to understand how different model characterization of TTDs and mean transit times affect multicriteria model performance. We demonstrate the importance of time variation in TTDs in simulating water movement along fast flow pathways, and investigate sensitivity of the models to assumptions about our ability to sample fast, near‐surface flow.