Modelling the future impacts of climate and land-use change on suspended sediment transport in the River Thames (UK)

The effects of climate change and variability on river flows have been widely studied. However the impacts of such changes on sediment transport have received comparatively little attention. In part this is because modelling sediment production and transport processes introduces additional uncertainty, but it also results from the fact that, alongside the climate change signal, there have been and are projected to be significant changes in land cover which strongly affect sediment-related processes. Here we assess the impact of a range of climatic variations and land covers on the River Thames catchment (UK). We first calculate a response of the system to climatic stressors (average precipitation, average temperature and increase in extreme precipitation) and land-cover stressors (change in the extent of arable land). To do this we use an ensemble of INCA hydrological and sediment behavioural models. The resulting system response, which reveals the nature of interactions between the driving factors, is then compared with climate projections originating from the UKCP09 assessment (UK Climate Projections 2009) to evaluate the likelihood of the range of projected outcomes. The results show that climate and land cover each exert an individual control on sediment transport. Their effects vary depending on the land use and on the level of projected climate change. The suspended sediment yield of the River Thames in its lowermost reach is expected to change by −4% (−16% to +13%, confidence interval, p = 0.95) under the A1FI emission scenario for the 2030s, although these figures could be substantially altered by an increase in extreme precipitation, which could raise the suspended sediment yield up to an additional +10%. A 70% increase in the extension of the arable land is projected to increase sediment yield by around 12% in the lowland reaches. A 50% reduction is projected to decrease sediment yield by around 13%

Dynamic response of land use and river nutrient concentration to long-term climatic changes

The combined indirect and direct impacts of land use change and climate change on river water quality were assessed. A land use allocation model was used to evaluate the response of the catchment land use to long-term climatic changes. Its results were used to drive a water quality model and assess the impact of climatic alterations on freshwater nitrate and phosphorus concentrations. Climatic projections were employed to estimate the likelihood of such response. The River Thames catchment (UK) was used as a case-study. If land use is considered as static parameter, according to the model results, climate change alone should reduce the average nitrate concentration, although just by a small amount, by the 2050s in the Lower Thames, due to reduced runoff (and lower export of nitrate from agricultural soils) and increased instream denitrification, and should increase the average phosphorus concentration by 12% by the 2050s in the Lower Thames, due to a reduction of the effluent dilution capacity of the river flow. However, the results of this study also show that these long-term climatic alterations are likely to lead to a reduction in the arable land in the Thames, replaced by improved grassland, due to a decrease in agriculture profitability in the UK. Taking into account the dynamic co-evolution of land use with climate, the average nitrate concentration is expected to be decreased by around 6% by the 2050s in both the upper and the lower Thames, following the model results, and the average phosphorus concentration increased by 13% in the upper Thames and 5% in the lower Thames. On the long term (2080s), nitrate is expected to decrease by 9% and 8% (upper and lower Thames respectively) and phosphorus not to change in the upper thames and increase by 5% in the lower Thames

Assessment of risks to public water supply from low flows and harmful water quality in a changing climate

Water resources planning and management by water utilities have traditionally been based on consideration of water availability. However, the reliability of public water supplies can also be influenced by the quality of water bodies. In this study, we proposed a framework that integrates the analysis of risks of inadequate water quality and risks of insufficient water availability. We have developed a coupled modeling system that combines hydrological modeling of river water quantity and quality, rules for water withdrawals from rivers into storage reservoirs, and dynamical simulation of harmful algal blooms in storage reservoirs. We use this framework to assess the impact of climate change, demand growth, and land‐use change on the reliability of public water supplies. The proposed method is tested on the River Thames catchment in the south of England. The results show that alongside the well‐known risks of rising water demand in the south of England and uncertain impacts of climate change, diffuse pollution from agriculture and effluent from upstream waste water treatment works potentially represent a threat to the reliability of public water supplies in London. We quantify the steps that could be taken to ameliorate these threats, though even a vigorous pollution‐prevention strategy would not be sufficient to offset the projected effects of climate change on water quality and the reliability of public water supplies. The proposed method can help water utilities to recognize their system vulnerability and evaluate the potential solutions to achieve more reliable water supplies. supplie

Using post-flood surveys and geomorphologic mapping to evaluate hydrological and hydraulic models: The flash flood of the Girona River (Spain) in 2007

This paper analyzes the Girona River (Spain) flash flood, occurred on the 12th of October 2007, combining hydrological and hydraulic modeling with geomorphologic mapping and post-flood survey information. This research aims to reproduce the flood event in order to understand and decipher the flood processes and dynamics on a system of prograding alluvial fans. The hydrological model TETIS was used to characterize the shape and dimension of the October 2007 Girona River hydrograph. Subsequently, the flood event was reproduced using the free surface flow module of the model RiverFlow2D. The combination of hydrological and hydraulic models was evaluated using post-flood surveys defining maximum flooded area and flood depths. Then, simulations with different peak discharges were carried out to estimate the hydro-geomorphologic response of the Girona River floodplain, through the identification of the activation thresholds in different geomorphic elements. Results showed that the unit peak discharge of the October 2007 flood event (5 m3 s−1 km−2) was among the largest ever recorded in the area, according to the existing literature. Likewise, the hydraulic model showed a good performance in reproducing the flood event (FitA = 76%, RMSE = 0.65 m and NSE = 0.6), despite the complexity of the case, an ephemeral and ungauged river. The model simulation revealed the existence of an activation pattern of paleochannels and alluvial fans, which was altered by the presence of some anthropogenic disturbances. This multidisciplinary approach proved to be a useful strategy for understanding flash flood processes in ungauged catchments. It allowed understanding the mechanisms governing floods in alluvial fans systems and it represented a solid contribution for early warning plans and risk mitigation policies.This collaborative research was financed with the projects CGL2013-44917-R and SLWAMED CGL2014-58127-C3-2, of the Ministry of Economy and Competitiveness of the Spanish Government. Both projects were co-financed with FEDER funds. The observed rainfall and water discharge records were provided by "Sistema Automatic de Information Hidrologica (SAIH)", which belongs to the CHJ (Spain). This work was also possible due to the kind cooperation of the members of the Plataforma Ciutadana Riu Girona and several anonymous farmers interviewed during the field works. We also thank two anonymous reviewers for their useful and thought-provoking comments.Segura-Beltrán, F.; Sanchis Ibor, C.; Morales-Hernández, M.; González-Sanchis, MDC.; Bussi, G.; Ortiz, E. (2016). Using post-flood surveys and geomorphologic mapping to evaluate hydrological and hydraulic models: The flash flood of the Girona River (Spain) in 2007. Journal of Hydrology. 541(Part A):310-329. https://doi.org/10.1016/j.jhydrol.2016.04.039S310329541Part

Impacts of climate change, land-use change and phosphorus reduction on phytoplankton in the River Thames (UK)

Potential increases of phytoplankton concentrations in river systems due to global warming and changing climate could pose a serious threat to the anthropogenic use of surface waters. Nevertheless, the extent of the effect of climatic alterations on phytoplankton concentrations in river systems has not yet been analysed in detail. In this study, we assess the impact of a change in precipitation and temperature on river phytoplankton concentration by means of a physically-based model. A scenario-neutral methodology has been employed to evaluate the effects of climate alterations on flow, phosphorus concentration and phytoplankton concentration of the River Thames (southern England). In particular, five groups of phytoplankton are considered, representing a range of size classes and pigment phenotypes, under three different land-use/land-management scenarios to assess their impact on phytoplankton population levels. The model results are evaluated within the framework of future climate projections, using the UK Climate Projections 09 (UKCP09) for the 2030s. The results of the model demonstrate that an increase in average phytoplankton concentration due to climate change is highly likely to occur, with the magnitude varying depending on the location along the River Thames. Cyanobacteria show significant increases under future climate change and land use change. An expansion of intensive agriculture accentuates the growth in phytoplankton, especially in the upper reaches of the River Thames. However, an optimal phosphorus removal mitigation strategy, which combines reduction of fertiliser application and phosphorus removal from wastewater, can help to reduce this increas

Impacts of climate change, land-use change and phosphorus reduction on phytoplankton in the River Thames (UK)

Potential increases of phytoplankton concentrations in river systems due to global warming and changing climate could pose a serious threat to the anthropogenic use of surface waters. Nevertheless, the extent of the effect of climatic alterations on phytoplankton concentrations in river systems has not yet been analysed in detail. In this study, we assess the impact of a change in precipitation and temperature on river phytoplankton concentration by means of a physically-based model. A scenario-neutral methodology has been employed to evaluate the effects of climate alterations on flow, phosphorus concentration and phytoplankton concentration of the River Thames (southern England). In particular, five groups of phytoplankton are considered, representing a range of size classes and pigment phenotypes, under three different land-use/land-management scenarios to assess their impact on phytoplankton population levels. The model results are evaluated within the framework of future climate projections, using the UK Climate Projections 09 (UKCP09) for the 2030s. The results of the model demonstrate that an increase in average phytoplankton concentration due to climate change is highly likely to occur, with the magnitude varying depending on the location along the River Thames. Cyanobacteria show significant increases under future climate change and land use change. An expansion of intensive agriculture accentuates the growth in phytoplankton, especially in the upper reaches of the River Thames. However, an optimal phosphorus removal mitigation strategy, which combines reduction of fertiliser application and phosphorus removal from wastewater, can help to reduce this increase in phytoplankton concentration, and in some cases, compensate for the effect of rising temperature

Sediment yield model implementation based on check dam infill stratigraphy in a semiarid Mediterranean catchment

Soil loss and sediment transport in Mediterranean areas are driven by complex non-linear processes which have been only partially understood. Distributed models can be very helpful tools for understanding the catchment-scale phenomena which lead to soil erosion and sediment transport. In this study, a modelling approach is proposed to reproduce and evaluate erosion and sediment yield processes in a Mediterranean catchment (Rambla del Poyo, Valencia, Spain). Due to the lack of sediment transport records for model calibration and validation, a detailed description of the alluvial stratigraphy infilling a check dam that drains a 12.9 km(2) sub-catchment was used as indirect information of sediment yield data. These dam infill sediments showed evidences of at least 15 depositional events (floods) over the time period 1990-2009. The TETIS model, a distributed conceptual hydrological and sediment model, was coupled to the Sediment Trap Efficiency for Small Ponds (STEP) model for reproducing reservoir retention, and it was calibrated and validated using the sedimentation volume estimated for the depositional units associated with discrete runoff events. The results show relatively low net erosion rates compared to other Mediterranean catchments (0.136 Mg ha(-1) yr(-1)), probably due to the extensive outcrops of limestone bedrock, thin soils and rather homogeneous vegetation cover. The simulated sediment production and transport rates offer model satisfactory results, further supported by in-site palaeohydrological evidences and spatial validation using additional check dams, showing the great potential of the presented data assimilation methodology for the quantitative analysis of sediment dynamics in ungauged Mediterranean basins.This study was funded by the Spanish Ministry of Economy and Competitiveness through the research projects FLOOD-MED (ref. CGL2008-06474-C02-01/02), SCARCE-CONSOLIDER (ref. CSD2009-00065), CLARIES (ref. CGL2011-29176) and ECO-TETIS (ref. CGL2011-28776-C02-01). The hydrometeorological data was provided by the Automatic Hydrological Information System of the Spanish Jucar River Authority (SAIH - Confederacion Hidrografica del Jucar). Wildfires information was provided by the Regional Government. We would also like to thank Artemi Cerda and the three anonymous referees for their useful comments which helped to improve the scientific quality of the paper.Bussi, G.; Rodríguez-Lloveras, X.; Francés, F.; Benito, G.; Sanchez-Moya, Y.; Sopeña, A. (2013). Sediment yield model implementation based on check dam infill stratigraphy in a semiarid Mediterranean catchment. Hydrology and Earth System Sciences. 17:3339-3354. doi:10.5194/hess-17-3339-2013S3339335417Ackermann, W. C. and Corinth, R. L.: An empirical equation for reservoir sedimentation, in Symposium of Bari (Italy), International Association of Hydrological Sciences Publication 59, 359–366, Bari (Italy), 1962.Alatorre, L. C., Beguería, S., and García-Ruiz, J. M.: Regional scale modeling of hillslope sediment delivery: A case study in the Barasona Reservoir watershed (Spain) using WATEM/SEDEM, J. Hydrol., 391, 109-123, https://doi.org/10.1016/j.jhydrol.2010.07.010, 2010.Alatorre, L. C., Beguer\\'ia, S., Lana-Renault, N., Navas, A., and Garc\\'ia-Ruiz, J. M.: Soil erosion and sediment delivery in a mountain catchment under scenarios of land use change using a spatially distributed numerical model, Hydrol. Earth Syst. Sci., 16, 1321–1334, https://doi.org/10.5194/hess-16-1321-2012, 2012.Andrés-Doménech, I., Múnera, J. C., Francés, F., and Marco, J. B.: Coupling urban event-based and catchment continuous modelling for combined sewer overflow river impact assessment, Hydrol. Earth Syst. Sci., 14, 2057–2072, https://doi.org/10.5194/hess-14-2057-2010, 2010.Andreu, V., Imeson, A. C., and Rubio, J. L.: Temporal changes in soil aggregates and water erosion after a wildfire in a Mediterranean pine forest, Catena, 44, 69–84, https://doi.org/10.1016/S0341-8162(00)00177-6, 2001.Antolín, C.: El suelo como recurso natural en la Comunitat Valenciana, Consellería de Territorio y Vivienda, Generalitat Valenciana, Valencia (Spain), 1998.Avendaño Salas, C., Cobo Rayán, R., Gómez Montaña, J., and Sanz Montero, M.: Procedimiento para evaluar la degradación específica (erosión) de cuencas de embalses a partir de los sedimientos acumulados en los mismos. Aplicación al estudio de embalses españoles, Ingeniería Civil, 99, 51–58, 1995.Avendaño Salas, N., Sanz Montero, M., Cobo Rayán, R., and Gómez Montaña, J.: Sediment yield at Spanish reservoirs and its relationship with the drainage basin area, Proceedings of the 19th Symposium of Large Dams, Florence, ICOLD (International Committee on Large Dams), Florence, 863–874, 1997.Baeza, M. J., Valdecantos, A., Alloza, J. A., and Vallejo, V. R.: Human disturbance and environmental factors as drivers of long-term post-fire regeneration patterns in Mediterranean forests, J. Veg. Sci., 18,, 243–252, https://doi.org/10.1111/j.1654-1103.2007.tb02535.x, 2007.Baker, V.: Paleoflood hydrology: Origin, progress, prospects, Geomorphology, 101, 1–13, https://doi.org/10.1016/j.geomorph.2008.05.016, 2008.Bangqi Hu, Zuosheng Yang, Houjie Wang, Xiaoxia Sun, Naishuang Bi, and Guogang Li: Sedimentation in the Three Gorges Dam and the future trend of Changjiang (Yangtze River) sediment flux to the sea, Hydrol. Earth Syst. Sci., 13, 2253–2264, https://doi.org/10.5194/hess-13-2253-2009, 2009.Bellin, N., Vanacker, V., Van Wesemael, B., Solé-Benet, A., and Bakker, M.: Natural and anthropogenic controls on soil erosion in the Internal Betic Cordillera (southeast Spain), Catena, 87, 190–200, https://doi.org/10.1016/j.catena.2011.05.022, 2011.Benito, G., Rico, M., Sánchez-Moya, Y., Sopeña, A., Thorndycraft, V. R., and Barriendos M.: The impact of late Holocene climatic variability and land use change on the flood hydrology of the Guadalentín River, southeast Spain, Global Planet. Change, 70, 53–63, https://doi.org/10.1016/j.gloplacha.2009.11.007, 2010.Boix-Fayos, C., Martínez-Mena, M., Calvo-Cases, A., Castillo, V., and Albaladejo, J.: Concise review of interrill erosion studies in SE Spain (Alicante and Murcia): erosion rates and progress of knowledge from the 1980s, Land Degrad. Dev., 16, 517–528, https://doi.org/10.1002/ldr.706, 2005.Boix-Fayos, C., De Vente, J., Martínez-Mena, M., Barberá, G., and Castillo, V.: The impact of land use change and check-dams on catchment sediment yield, Hydrol. Process., 22, 4922–4935, https://doi.org/10.1002/hyp.7115, 2008.Brown, C: Discussion of sedimentation in reservoir, In: Witzig J. (Ed.), Proceedings of the American Society of Civil Engineers 69, 1493–1500, 1943.Brune, G. M.: Trap efficiency of reservoirs, Trans. AGU, 34, 407–418, 1953.Callander, R. A. and Duder, J. N.: Reservoir sedimentation in the Rangitaiki River, New Zealand Engineering, 34, 208–215, 1979.Camarasa Belmonte, A. M. and Segura Beltrán, F.: Flood events in Mediterranean ephemeral streams (ramblas) in Valencia region, Spain, Catena, 45, 229–249, https://doi.org/10.1016/S0341-8162(01)00146-1, 2001.Campo, J., Andreu, V., Gimeno-Garcia, E., González, O., and Rubio, J. L.: Occurrence of soil erosion after repeated experimental fires in a Mediterranean environment, Geomorphology, 82, 376–387, https://doi.org/10.1016/j.geomorph.2006.05.014, 2006.Cerdà, A.: Seasonal changes of the infiltration rates in a Mediterranean scrubland on limestone, J. Hydrol., 198, 209–225, https://doi.org/10.1016/S0022-1694(96)03295-7, 1997.Cerdà, A.: Soil aggregate stability under different Mediterranean vegetation types, Catena, 32, 73–86, https://doi.org/10.1016/S0341-8162(98)00041-1, 1998a.Cerdà, A.: Changes in overland flow and infiltration after a rangeland fire in a Mediterranean scrubland, Hydrol. Process., 12, 1031–1042, https://doi.org/10.1002/(SICI)1099-1085(19980615)12:7 3.0.CO;2-V, 1998bCerdà, A.: Post-fire dynamics of erosional processes under Mediterranean climatic conditions, Z. Geomorphologie, 42, 373–398, 1998c.Cerdà, A. and Doerr, S. H.: The effect of ash and needle cover on surface runoff and erosion in the immediate post-fire period, Catena, 74, 256–263, https://doi.org/10.1016/j.catena.2008.03.010, 2008.Cerdà, A. and Lasanta, T.: Long-term erosional responses after fire in the Central Spanish Pyrenees, Catena, 60, 59–80, https://doi.org/10.1016/j.catena.2004.09.006, 2005.Chen, C.: Design of sediment retention basins, in Proceedings, National Symposium on Urban Hydrology and Sediment Control, 285–298, University of Kentucky, Lexington, KY, 1975.Cheng, Y.: Sediment discharge from a storm-water retention pond, J. Irrig. Drain. Eng., 134, 606–612, https://doi.org/10.1061/(ASCE)0733-9437(2008)134:5(606), 2008.Coulthard, T. J., Kirkby, M. J., and Macklin, M.G.: Non-linearity and spatial resolution in a cellular automaton model of a small upland basin, Hydrol. Earth. Syst. Sci., 2, 257-264, 1998.De Vente, J., Poesen, J., and Verstraeten, G.: The application of semi-quantitative methods and reservoir sedimentation rates for the prediction of basin sediment yield in Spain, J. Hydrol., 305, 63–86, https://doi.org/10.1016/j.jhydrol.2004.08.030, 2005.De Vente, J., Poesen, J., Verstraeten, G., Van Rompaey, A., and Govers, G.: Spatially distributed modelling of soil erosion and sediment yield at regional scales in Spain, Global Planet. Change, 60, 393–415, https://doi.org/10.1016/j.gloplacha.2007.05.002, 2008.Dissmeyer, G. E. and Foster, G. R.: A guide for predicting sheet and rill erosion on forest land, USDA, Forest Service, Southern Region, Atlanta, Ga. (USA), 1984.Duan, Q., Sorooshian, S., and Gupta, V.: Effective and efficient global optimization for conceptual rainfall-runoff models, Water Resour. Res., 28, 1015–1031, https://doi.org/10.1029/91WR02985, 1992.Duan, Q., Sorooshian, S., and Gupta, V.: Optimal use of the SCE-UA global optimization method for calibrating watershed models, J. Hydrol., 158, 265–284, https://doi.org/10.1016/0022-1694(94)90057-4, 1994.Duck, R. and McManus, J.: Sedimentation in natural and artificial Impoundments: an indicator of evolving climate, land use and dynamic conditions, in: Geomorphology and Sedimentology of Lakes and Reservoirs, edited by: McManus J. and Duck R., Wiley, 1993.Engelund, F. and Hansen, E.: A monograph on sediment transport in alluvial streams, Monogr, Denmark Tech Univ., Hydraul Lab, 1967.Farnham, C. W., Beer, C. E., and Heinemann, H.: Evaluation of factors affecting reservoir sediment deposition, in Symposium of Garda (Italy): Hydrology of Lakes and Reservoirs, International Association of Hydrological Sciences Publication, 747–758, Garda (Italy), 1966.Foster, I.: Lakes and Reservoirs in the Sediment Delivery System: Reconstructing Sediment Yields, in: Soil erosion and sediment redistribution in river catchments. Measurement, Modelling and Management, edited by: Owens P. and Collins A., Biddles Ltd, King's Lynn, p. 328, https://doi.org/10.1079/9780851990507.0128, 2006.Foster, I. and Walling, D.: Using reservoir deposits to reconstruct changing sediment yields and sources in the catchment of the Old Mill Reservoir, South Devon, UK, over the past 50 years, Hydrolog. Sci. J., 39, 347–368, https://doi.org/10.1080/02626669409492755, 1994.Francés, F., Vélez, J. J., Vélez, J. I., and Puricelli, M.: Distributed modelling of large basins for a real time flood forecasting system in Spain, Proceedings Second Federal Interagency Hydrologic Modelling Conference, Gan, TY and Biftu, Las Vegas, 3513–3524, 2002.Francés, F., Vélez, J. I., and Vélez J. J.: Split-parameter structure for the automatic calibration of distributed hydrological models, J. Hydrol., 332, 226–240, https://doi.org/10.1016/j.jhydrol.2006.06.032, 2007.Francés, F., García-Bartual, R., and Bussi, G.: High return period annual maximum reservoir water level quantiles estimation using synthetic generated flood events, in Risk Analysis, Dam Safety, Dam Security and Critical Infrastructure Management, 185–190, Taylor & Francis Group, London, 2011.Gallart, F., Balasch, C., Regüés, D., Soler, M., and Castelltort, X.: Catchment dynamics in a Mediterranean mountain environment: the Vallcebre research basins (South Eastern Pyrenees), II Erosion and sediment dynamics, Catchment dynamics and river processes: latest research with examples from the Mediterranean climate regions, Elsevier, 17–29, 2005.Geiger, A. F.: Sediment yields from small watersheds in the United States, 11th General Assembly of the International Union of Geodesy and Geophysics, Vol. 1, 269–276, Toronto (Canada), 1957.González-Hidalgo, J. C., Peña-Monné, J. L., and De Luis, M.: A review of daily soil erosion in Western Mediterranean areas, Catena, 71, 193–199, https://doi.org/10.1016/j.catena.2007.03.005, 2007.Grauso, S., Fattoruso, G., Crocetti, G., and Montanari, A.: Estimating the suspended sediment yield in a river network by means of geomorphic parameters and regression relationships, Hydrol. Earth. Syst. Sci., 12, 177–191, https://doi.org/10.5194/hess-13-1937-2009, 2008.Johnson, B. E., Julien, P. Y., Molnar, D. K., and Watson, C. C.: The two-dimensional upland erosion model CASC2D-SED, J. Am. Water Resour. As., 36, 31–42, https://doi.org/10.1111/j.1752-1688.2000.tb04246.x, 2000.Julien, P. Y.: Erosion and sedimentation, second edition, Cambridge University Press, 2010.Julien, P. and Simons, D. B.: Sediment transport capacity of overland flow, Transactions of the ASAE, 1985.Jolly, J.: A proposed method for accurately calculating sediment yields from reservoir deposition volumes, Proceedings of the Exeter Symposium, IAHS Publ. No 37, 1982.Kilinc, M. and Richardson, E. V.: Mechanics of soil erosion from overland flow generated by simulated rainfall, Colorado State University, Hydrology Papers, 1973.Kirkby, M., Irvine, B., Jones, R., and Govers G.: The PESERA coarse scale erosion model for Europe. I. Model rationale and implementation, Eur. J. Soil Sci., 59, 1293–1306, https://doi.org/10.1111/j.1365-2389.2008.01072.x, 2008.Kochel, R. and Baker, V.: Paleoflood Hydrology, Science, 215, 353–361, https://doi.org/10.1126/science.215.4531.353, 1982.Kosmas, C., Danalatos, N. G., Cammeraat, L. H., Chabart, M., Diamantopoulos, J., Farand, R., Gutierrez, L., Jacob, A., Marques, H., Martinez-Fernandez, J., Mizara, A., Moustakas, N., Nicolau, J. M., Oliveros, C., Pinna, G., Puddu, R., Puigdefabregas, J., Roxo, M., Simao, A., Stamou, G., Tomasi, N., Usai, D., and Vacca, A.: The effect of land use on runoff and soil erosion rates under Mediterranean conditions, Catena, 29, 45–59, 1997.Lane, E. and Koelzer, V.: Density of sediments deposited in reservoirs, Rep. No. 9 of a Study of Methods Used in Measurement and Analysis of Sediment Loads in Streams, 1943.Le Roux, J. and Roos, Z.: The rate of soil erosion in the Wuras Dam catchment calculated from sediments trapped in the dam, Z. Geomorphol, Suppl. 26, 315–329, 1982.Machado, M. J., Benito, G., Barriendos, M., and Rodrigo, F. S.: 500 years of rainfall variability and extreme hydrological events in southeastern Spain drylands, J. Arid Environ., 75, 1244–1253, https://doi.org/10.1016/j.jaridenv.2011.02.002, 2011.McManus, J. and Duck, R: Sediment yield estimated from reservoir siltation in the Ochil Hills, Scotland, Earth Surf. Proc. Land, 10, 193–200, https://doi.org/10.1002/esp.3290100211, 1985.Montoya, J. J.: Desarrollo de un modelo conceptual de producción, transporte y depósito de sedimentos, Phd Thesis. Universitat Politècnica de València (Spain), 2008.Morales de la Cruz M. and Francés, F.: Hydrological modelling of the "Sierra de las Minas" in Guatemala, by using a conceptual distributed model and considering the lack of data, WITpress, 97–108, 2008.Moriasi, D., Arnold, J., Van Liew, M. W., Bingner, R., Harme, R., and Veith, T.: Model evaluation guidelines for systematic quantification of accuracy in watershed simulations, T. ASAE, 50, 885–900, 2007.Nash, J. E. and Sutcliffe, J. V.: River flow forecasting through conceptual models – Part 1 – A discussion of principles, J. Hydrol., 10, 282–290, https://doi.org/10.1016/0022-1694(70)90255-6, 1970.Nehyba, S., Nývlt., D., Schkade, U., Kirchner, G., and Francu, E.: Depositional rates and dating techniques of modern deposits in the Brno reservoir (Czech Republic) during the last 70 years, J. Paleolimnol., 45, 41–55, https://doi.org/10.1007/s10933-010-9478-5, 2011.Neil, D. and Mazari, R.: Sediment yield mapping using small dam sedimentation surveys, Southern Tablelands, New South Wales, Catena, 20, 13–25, https://doi.org/10.1016/0341-8162(93)90026-L, 1993.Ogden, F. L. and Heilig, A.: Two-dimensional watershed-scale erosion modeling with CASC2D, Landscape Erosion and Evolution Modeling, (RS Harmon and WW Doe III, eds.), Kluwer Academic Publishers, New York, ISBN 0-306-4618-6, 2001.Phillips, C. J. and Nelson, C. S.: Sedimentation in an artifical lake – Lake Matahina, Bay of Plenty, New Zeal. J. Mar. Fresh, 15, 459–473, https://doi.org/10.1080/00288330.1981.9515938, 1981.Piest, R. F., Bradford, J. M., and Wyatt, G. M.: Soil erosion and sediment transport from gullies, J. Hydr. Eng. Div-ASCE, 101, 65–80, 1975.Prosser, I. P. and Rustomji, P.: Sediment transport capacity relations for overland flow, Prog. Phys. Geogr., 24, 179–193, https://doi.org/10.1177/030913330002400202, 2000.Prosser, I. and Williams, L.: The effect of wildfire on runoff and erosion in native Eucalyptus forest, Hydrol. Process., 12, 251–265, https://doi.org/10.1002/(SICI)1099-1085(199802)12:2< 251::AID-HYP574>3.0.CO;2-4, 1998.Rey-Benayas, J. M., Martins, A., Nicolau, J. M., and Schulz, J.: Abandonment of agricultural land: an overview of drivers and consequences, CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources, 2, 057, https://doi.org/10.1079/PAVSNNR20072057, 2007.Roering, J. J., Kirchner, J. W., and Dietrich, W. E.: Evidence for nonlinear, diffusive sediment transport on hillslopes and implications for landscape morphology, Water Resour. Res., 35, 853–870, https://doi.org/10.1029/1998WR900090, 1999.Rohel, J. W.: Sediment source areas, delivery ratios, and influencing morphological factors, in Symposium of Bari (Italy), International Association of Hydrological Sciences Publication 59, 202–213, Bari (Italy), 1962.Rojas, R.: GIS-based upland erosion modeling, geovisualization and grid size effects on erosion simulations with CASC2D-SED, PhD Thesis, Colorado State University, 2002.Romero-Díaz, A., Alonso-Sarriá, F., and Martínez-Lloris, M.: Erosion rates obtained from check-dam sedimentation (SE Spain). A multi-method comparison, Catena, 71, 172–178, https://doi.org/10.1016/j.catena.2006.05.011, 2007.Rubio, J. L., Sánchez, J., and Forteza, J.: Proyecto LUCDEME. Mapa de suelos de la Comunidad Valenciana, 1995.Rulli, M., Spada, M., Bozzi, S., Bocchiola, D. and Rosso, R.: Modelling sediment yield in burned areas, in: Sediment budgets: proceedings of the International Symposium on Sediment Budgets: held during the Seventh Scientific Assembly of the International Association of Hydrological Sciences (IAHS), edited by: Horowitz, A. and Walling, D., IAHS Publ. No 292, Foz do Iguaço (Brazil), 162–170, 2005.Salazar, S., Francés, F., Komma, J., Blume, T., Francke, T., Bronstert, A., and Blöschl, G.: A comparative analysis of the effectiveness of flood management measures based on the concept of "retaining water in the landscape" in different European hydro-climatic regions, Nat. Hazards Earth Syst. Sci., 12, 3287–3306, https://doi.org/10.5194/nhess-12-3287-2012, 2013.Saxton, K. E. and Rawls, W. J.: Soil water characteristic estimates by texture and organic matter for hydrologic solutions, Soil Sci. Soc. Am. J., 70, 1569–1578, https://doi.org/10.2136/sssaj2005.0117, 2006.Shakesby, R.: Post-wildfire soil erosion in the Mediterranean: Review and future research directions, Earth-Sci. Rev., 105, 71–100, https://doi.org/10.1016/j.earscirev.2011.01.001, 2011.Shumm, S. and Lichty, R.: Time, space and causality in geomorphology, Am. J. Sci., 263, 110–119, https://doi.org/10.2475/ajs.263.2.110, 1965.Sougnez, N., Van Wesemael, B., and Vanacker, V.: Low erosion rates measured for steep, sparsely vegetated catchments in southeast Spain, Catena, 84, 1–11, https://doi.org/10.1016/j.catena.2010.08.010, 2011.Van den Wall Blake, G.: Siltation and soil erosion survey in Zimbabwe, in: Drainage basin sediment delivery (proceedings of the Albuquerque symposium, August 1986), edited by: Hadley, R., IAHS Publication 159, 69–80, 1986.Van Rompaey, A., Verstraeten, G., Van Oost, K., Govers, G., and Poesen, J.: Modelling mean annual sediment yield using a distributed approach, Earth Surf. Proc. Land, 26, 1221–1236, https://doi.org/10.1002/esp.275, 2001.Van Rompaey, A., Vieillefont, V., Jones, R., Montanarella, L., Verstraeten, G., Bazzoffi, P., Dostal, T., Krasa, J., De Vente, J., and Poesen, J.: Validation of soil erosion estimates at European scale, European Soil Bureau Research Report No.13, EUR 20827 EN, Office for Official Publications of the European Communities, Luxembourg, 2003.Verstraeten, G. and Poesen, J.: Estimating trap efficiency of small reservoirs and ponds: methods and implications for the assessment of sediment yield, Prog. Phys. Geogr., 24, 219–251, https://doi.org/10.1177/030913330002400204, 2000.Verstraeten, G. and Poesen, J.: Modelling the long-term sediment trap efficiency of small ponds, Hydrol. Process., 15, 2797–2819, https://doi.org/10.1002/hyp.269, 2001.Verstraeten, G. and Poesen, J.: Using sediment deposits in small ponds to quantify sediment yield from small catchments: possibilities and limitations, Earth Surf. Proc. Land, 27, 1425–1439, https://doi.org/10.1002/esp.439, 2002.Verstraeten, G., Poesen, J., De Vente, J., and Koninckx, X.: Sediment yield variability in Spain: a quantitative and semiqualitative

Ecotoxicity of microplastics to freshwater biota: Considering exposure and hazard across trophic levels

In contrast to marine ecosystems, the toxicity impact of microplastics in freshwater environments is poorly understood. This contribution reviews the literature on the range of effects of microplastics across and between trophic levels within the freshwater environment, including biofilms, macrophytes, phytoplankton, invertebrates, fish and amphibians. While there is supporting evidence for toxicity in some species e.g. growth reduction for photoautotrophs, increased mortality for some invertebrates, genetic changes in amphibians, and cell internalization of microplastics and nanoplastics in fish; other studies show that it is uncertain whether microplastics can have detrimental long-term impacts on ecosystems. Some taxa have yet to be studied e.g. benthic diatoms, while only 12% of publications on microplastics in freshwater, demonstrate trophic transfer in foodwebs. The fact that just 2% of publications focus on microplastics colonized by biofilms is hugely concerning given the cascading detrimental effects this could have on freshwater ecosystem function. Multiple additional stressors including environmental change (temperature rises and invasive species) and contaminants of anthropogenic origin (antibiotics, metals, pesticides and endocrine disruptors) will likely exacerbate negative interactions between microplastics and freshwater organisms, with potentially significant damaging consequences to freshwater ecosystems and foodwebs

Impact of dams and climate change on suspended sediment flux to the Mekong delta

The livelihoods of millions of people living in the world's deltas are deeply interconnected with the sediment dynamics of these deltas. In particular a sustainable supply of fluvial sediments from upstream is critical for ensuring the fertility of delta soils and for promoting sediment deposition that can offset rising sea levels. Yet, in many large river catchments this supply of sediment is being threatened by the planned construction of large dams. In this study, we apply the INCA hydrological and sediment model to the Mekong River catchment in South East Asia. The aim is to assess the impact of several large dams (both existing and planned) on the suspended sediment fluxes of the river. We force the INCA model with a climate model to assess the interplay of changing climate and sediment trapping caused by dam construction. The results show that historical sediment flux declines are mostly caused by dams built in PR China and that sediment trapping will increase in the future due to the construction of new dams in PDR Lao and Cambodia. If all dams that are currently planned for the next two decades are built, they will induce a decline of suspended sediment flux of 50% (47–53% 90% confidence interval (90%CI)) compared to current levels (99 Mt/year at the delta apex), with potentially damaging consequences for local livelihoods and ecosystems