Vegetation canopy changes and use of SoilGrids data for assessing the effect of extreme rains on annual soil losses

Extreme rains can trigger natural hazard processes such as soil erosion, land sliding and flash floods. Climate change studies show that the frequency of extreme rains is in an increasing trend, resulting in the amplification of hazard processes. For assessing the magnitude of soil losses various models are available. While annual empirical models (e.g. USLE, RUSLE, MMF) are easy to use, they do not take into account the effect of extreme rains. The event based models (e.g. LISEM, WEPP) can simulate erosion processes in detail, but rainfall event data is simply not available everywhere. To solve this problem, Shrestha and Jetten, (2018)have developed a daily erosion model and demonstratedthat the effect of extreme rains can be incorporated easily in annual estimates. For running the model, daily rainfall, vegetation canopy changes, topography and soil dataare required. Daily vegetation canopy changes mapping is a challenge and soil data may not be available easily everywhere due to higher cost involved in soil survey. Recently, time series NDVI and SoilGrids data are available freely, solving data scarcity problem. But, we do not know how good is the data for hazard assessment. The objectives of the study are in assessing the effect of daily canopy coverchanges on rain interception, and in the use of SoilGrids data for erosion estimation.The study area is located in Sehoul, Morocco. Time series NDVI data at 1 Km resolution was obtainedfrom Vito, Belgium (http://free.vgt.vito.be), and resampled to 15mand at daily time step. Similarly, SoilGrids data at 250 m resolution was downloaded from ISRIC, The Netherlands (https://soilgrids.org). Pedotransfer functions were used to generate soil parameters and the daily erosion model was applied to assess soil losses. The results show that vegetation canopy cover plays an important role in the magnitude of soil losses. Canopy cover intercepts rain and protects the soil from raindrop impact. When canopy cover is lower, erosion rates are higher. During extreme rains, erosion can be very severe. The study shows that SoilGrids is a useful data source, and can be applied in daily erosion assessment in the semi-arid environment. The results also showthat daily erosion modelling gives better picture of annual soil losses since the effects of extreme rains are also incorporated

What is wrong with post‐fire soil erosion modelling? A meta‐analysis on current approaches, research gaps, and future directions

In the near future, a higher occurrence of wildfires is expected due to climate change, carrying social, environmental, and economic implications. Such impacts are often associated with an increase of post‐fire hydrological and erosive responses, which are difficult to predict. Soil erosion models have been proven to be a valuable tool in the decision‐making process, from emergency response to long‐term planning, however, they were not designed for post‐fire conditions, so they need to be adapted to include fire‐induced changes. In the recent years, there has been an increasing number of studies testing different models and adaptations for the prediction of post‐fire soil erosion. However, many of these adaptations are being applied without field validation or model performance assessment. Therefore, this study aims to describe the scientific advances in the last twenty years in post‐fire soil erosion modelling research and evaluate model adaptations to burned areas that aim to include: i) fire‐induced changes in soil and ground cover, ii) fire‐induced changes in infiltration, iii) burn severity, and iv) mitigation measures in their predictions. This study also discusses the strengths and weaknesses of those approaches, suggests potential improvements, and identifies directions for future research. Results show that studies are not homogeneously distributed worldwide, neither according to the model type used, nor by regions most affected by wildfires. During calibration, 73% of the cases involved model adaptation to burned conditions, and only 21% attempted to accommodate new processes. Burn severity was addressed in 75% of the cases, whilst mitigation measures were simulated in 27%. Additionally, only a minor percentage of model predictions were validated with independent field data (17%) or assessed for uncertainties (13%). Therefore, further efforts are required on the adaptation of erosion models to burned conditions to be widely used for post‐fire management decision.publishe

Semantic array programming in data-poor environments: assessing the interactions of shallow landslides and soil erosion

This research was conducted with the main objective to better integrate and quantify the role of water-induced shallow landslides within soil erosion processes, with a particular focus on data-poor conditions. To fulfil the objectives, catchment-scale studies on soil erosion by water and shallow landslides were conducted. A semi-quantitative method that combines heuristic, deterministic and probabilistic approaches is here proposed for a robust catchment-scale assessment of landslide susceptibility when available data are scarce. A set of different susceptibility-zonation maps was aggregated exploiting a modelling ensemble. Each susceptibility zonation has been obtained by applying heterogeneous statistical techniques such as logistic regression (LR), relative distance similarity (RDS), artificial neural network (ANN), and two different landslide-susceptibility techniques based on the infinite slope stability model. The good performance of the ensemble model, when compared with the single techniques, make this method suitable to be applied in data-poor areas where the lack of proper calibration and validation data can affect the application of physically based or conceptual models. A new modelling architecture to support the integrated assessment of soil erosion, by incorporating rainfall induced shallow landslides processes in data-poor conditions, was developed and tested in the study area. This proposed methodology is based on the geospatial semantic array programming paradigm. The integrated data-transformation model relies on a modular architecture, where the information flow among modules is constrained by semantic checks. By analysing modelling results within the study catchment, each year, on average, mass movements are responsible for a mean increase in the total soil erosion rate between 22 and 26% over the pre-failure estimate. The post-failure soil erosion rate in areas where landslides occurred is, on average, around 3.5 times the pre-failure value. These results confirm the importance to integrate landslide contribution into soil erosion modelling. Because the estimation of the changes in soil erosion from landslide activity is largely dependent on the quality of available datasets, this methodology broadens the possibility of a quantitative assessment of these effects in data-poor regions

Why increased extreme precipitation under climate change negatively affects water security

An increase in extreme precipitation is projected for many areas worldwide in the coming decades. To assess the impact of increased precipitation intensity on water security, we applied a regional-scale hydrological and soil erosion model, forced with regional climate model projections. We specifically considered the impact of climate change on the distribution of water between soil (green water) and surface water (blue water) compartments. We show that an increase in precipitation intensity leads to a redistribution of water within the catchment, where water storage in soil decreases and reservoir inflow increases. This affects plant water stress and the potential of rainfed versus irrigated agriculture, and increases dependency on reservoir storage, which is potentially threatened by increased soil erosion. This study demonstrates the crucial importance of accounting for the fact that increased precipitation intensity leads to water redistribution between green and blue water, increased soil erosion, and reduced water security. Ultimately, this has implications for design of climate change adaptation measures, which should aim to increase the water holding capacity of the soil (green water) and to maintain the storage capacity of reservoirs (blue water), benefiting rainfed and irrigated agriculture.</p

Improved water and land management in the Ethiopian highlands: its impact on downstream stakeholders dependent on the Blue Nile; Intermediate Results Dissemination Workshop February 5-6, 2009, Addis Ababa, Ethiopia

River basin management, Watershed management, Farming systems, Water balance, Reservoirs, Water supply, Irrigation requirements, Irrigation programs, Simulation models, Sedimentation, Rainfall-Runoff relationships, Erosion, Soil water, Water balance, Soil conservation, Institutions, Organizations, Policy, Water governance, International waters, Institutional and Behavioral Economics, Land Economics/Use, Resource /Energy Economics and Policy,

Modeling the spatial and temporal trends of water quality in boreal managed watersheds

Land use changes have altered natural hydrological pathways and biogeochemical cycling of carbon, nitrogen and phosphorus, among other elements, affecting the quality of aquatic ecosystems such as rivers, lakes and coastal areas. In this dissertation, the spatial and temporal trends of water quality variation in Finnish managed watersheds was studied by applying methods of multivariate statistics, time-series analysis, ecohydrological modeling and high-resolution geospatial data. The results show the complex effects of current land use, particularly agriculture, on stream water quality. New emerging trends of nutrient concentrations and loads were detected in the time-series analysis, such as an increase in the concentrations and loads of dissolved reactive phosphorus and total nitrogen, and a decrease in suspended sediment concentration in streams. This might be linked to the current erosion reduction strategy of land management for water protection. An ecohydrological modeling assessment showed an increasing downstream nutrient export from agricultural watershed under climate change scenarios. The modeling results also showed a potential nutrient export reduction by restoring potential biogeochemical hotspot areas - wet areas or areas prone to water saturation. These areas can function as nutrient sinks and enhance the watershed resiliency. High-resolution geospatial data allowed easier and more accurate mapping of wet areas as well as the extracting of their hydraulic characteristics. However, the ecohydrological models involved several sources of uncertainties, which need to be carefully addressed with extensive observational data, expert knowledge of model parameter definitions, proper modeling unit selection and empirical knowledge of the functioning of the studied watershed system. The results of this dissertation highlight the importance of combined methods for watershed management research, and the proper identification of the biophysical processes in the modeling of non-point pollutant sources; this can in turn lead to an efficient water protection measure, and restoring biogeochemical hotspot areas within the watershed.Vedenlaadun alueellisten ja ajallisten vaihteluiden mallintaminen viileän vyöhykkeen valuma-alueilla. Maankäytön muutokset ovat vaikuttaneet luonnollisiin hydrologisiin prosesseihin sekä hiilen, typen ja fosforin biogeokemiallisiin kiertoihin. Nämä puolestaan vaikuttavat vesiekosysteemien tilaan joissa, järvissä ja rannikkoalueella. Väitöstutkimuksessa tutkittiin vedenlaadun alueellisia ja ajallisia muutoksia suomalaisessa maaseutumaisemassa käyttäen monimuuttujamenetelmiä, aikasarja-analyysejä, ekohydrologista mallinnusta ja erotuskyvyltään tarkkoja paikkatietoaineistoja. Tulokset todentavat maatalouteen kytkeytyvien maankäytön piirteiden kompleksisia vaikutuksia jokivesien laatuun. Aikasarja-analyysit osoittivat myös aiemmin tuntemattomia trendejä jokivesien ravinteiden määrissä ja pitoisuuksissa, esimerkkeinä liuenneen reaktiivisen fosforin määrän ja pitoisuuden lisääntyminen sekä sedimenttisuspension väheneminen; molemmat eroosion vähentämiseen tähtäävien vesiensuojelutoimien seurauksena. Ekohydrologinen mallinnus osoitti myös sen, että ravinteiden huuhtoutuminen maatalousvaltaisilla valuma-alueilla lisääntyy ilmastonmuutoksen seurauksena. Tulokset kannustavat biogeokemiallisten avainalueiden, kuten kosteikkojen ja vettä keräävien painanteiden kunnostamiseen, jolloin ravinteiden huuhtoutuminen vähenee. Ravinnenieluina toimiessaan ne voivat myös parantaa valumaalueen ekologista kestävyyttä ja palautumiskykyä. Tutkimuksessa osoitettiin myös erotuskyvyltään tarkkojen paikkatietoaineistojen hyödyllisyys avainalueiden kartoituksessa ja alueiden hydrologisten ominaisuuksien tunnistamisessa. Ekohydrologiseen mallinnukseen sisältyy toisaalta myös epävarmuustekijöitä, joihin tulisi paneutua vielä kattavammin hyödyntäen asiantuntijatietoa parametrien täsmentämisessä, määrittämällä tarkennettuja mallinnusyksiköitä tai hyödyntäen empiirisiä tutkimustietoja valuma-alueen toiminnasta. Väitöstutkimus osoittaa myös sen, miten erilaisten tutkimusmenetelmien yhdistely vahvistaa valuma-aluetarkastelua ja siihen liittyen erilaisten biofysikaalisten prosessien ymmärtämistä ja keskeisten päästölähteiden mallintamista. Näin muodoin yhdistelmämenetelmien käyttö tukee entistä tehokkaampien vesiensuojelutoimien kehittämistä ja valumaalueiden biogeokemiallisten avainalueiden kunnostamistaModelado de las tendencias temporales y espaciales de la calidad del agua en cuencas hidrográficas boreales manejados. El cambio del uso del suelo ha alterado los procesos hidrológicos naturales y los ciclos biogeoquímicos del carbono, el nitrógeno y el fósforo, entre otros elementos, afectando directamente la calidad de los ecosistemas acuáticos como los ríos, lagos y zonas costeras. En esta disertación, las tendencias espaciales y temporales de la variación de la calidad del agua en cuencas hidrográficas finlandesas se estudiaron mediante la aplicación de métodos de estadística multivariante, análisis de series de tiempo, modelos ecohidrológicos y datos geoespaciales de alta resolución. Los resultados muestran los efectos complejos del uso actual del suelo, particularmente la agricultura, en la calidad del agua de los ríos y corrientes. Se detectaron nuevas tendencias emergentes de concentraciones y cargas de nutrientes en el análisis de series temporales, como un aumento en la concentración y carga del fósforo disuelto reactive y nitrógeno total, y una disminución en la concentración de sedimentos en suspensión en los ríos y corrientes. Esto podría estar vinculado a la estrategia actual de manejo del suelo, orientado a la reducción de la erosión para la protección del agua. Una evaluación a través de modelización ecohidrológica mostró un aumento de la exportación de nutrientes aguas abajo de la cuenca agrícola bajo escenarios de cambio climático. Los resultados de la modelización también mostraron una posible reducción de la exportación de nutrientes mediante la restauración de posibles zonas críticas biogeoquímicas: áreas húmedas o áreas propensas a la saturación de agua. Estas áreas pueden funcionar como sumideros de nutrientes y mejorar la resiliencia de la cuenca. Los datos geoespaciales de alta resolución permitieron un fácil y más preciso cartografiado de las áreas húmedas, así como la extracción de sus características hidráulicas. Sin embargo, los modelos ecohidrológicos involucraron varias fuentes de incertidumbre, que deben abordarse cuidadosamente con bastantes datos de observación, conocimiento experto de las definiciones de los parámetros del modelo, selección adecuada de la unidad de modelado y conocimiento empírico del funcionamiento del sistema de la cuenca estudiada. Los resultados de esta disertación destacan la importancia de los métodos combinados para la investigación de gestión de cuencas hidrográficas y la identificación adecuada de los procesos biofísicos en la modelización de fuentes contaminantes difusas; esto a su vez puede conducir a una medidaeficiente de protección del agua, y restauración de áreas claves de alta función biogeoquímica dentro de la cuenca

Impacts of Landscape Change on Water Resources

Changes in land use and land cover can have many drivers, including population growth, urbanization, agriculture, demand for food, evolution of socio-economic structure, policy regulations, and climate variability. The impacts of these changes on water resources range from changes in water availability (due to changes in losses of water to evapotranspiration and recharge) to degradation of water quality (increased erosion, salinity, chemical loadings, and pathogens). The impacts are manifested through complex hydro-bio-geo-climate characteristics, which underscore the need for integrated scientific approaches to understand the impacts of landscape change on water resources. Several techniques, such as field studies, long-term monitoring, remote sensing technologies, and advanced modeling studies, have contributed to better understanding the modes and mechanisms by which landscape changes impact water resources. Such research studies can help unlock the complex interconnected influences of landscape on water resources in terms of quantity and quality at multiple spatial and temporal scales. In this Special Issue, we published a set of eight peer-reviewed articles elaborating on some of the specific topics of landscape changes and associated impacts on water resources

Connectivity elements and mitigation measures in policy-relevant soil erosion models: A survey across Europe

The current use of soil erosion models in Europe was investigated through an exploratory survey of 46 model applications covering 18 European countries. This revealed novel information on erosion model applications, their parameterisation, incorporation of landscape elements and mitigation measures with implications for connectivity and their use in decision-making in Europe. The model application predictions were applied at national, regional, catchment or field scale. The majority of model applications used the USLE or versions thereof, but a range of semi-empirical, decision-tree and process-based models were also used. The majority of model applications were used for policy relevant purposes such as erosion risk assessment or mitigation measure implementation at a range of spatial scales. The analysis identified an evident prevalence towards the use of national or regional data sets and a highly varying parameterisation of model applications. Landscape elements and mitigation measures with effects on connectivity were implemented in most model applications, but not with a focus on modelling connectivity within the landscape. Altogether, the results demonstrate a need for improving connectivity modelling in diverse agricultural landscapes across multiple scales. Models should be chosen dependent on their ability to reflect erosion risk at different spatial scales. Albeit, harmonisation of data sets, parameterisation procedures and validation approaches is needed for certain modelling scenarios to ensure comparability of soil erosion risk assessment and suitable mitigation practices. Furthermore, we recommend that policy-relevant erosion risk maps should be verified by empirical data and thresholds derived from erosion risk maps should be adapted to regional conditions when used for policy guidelines. Hence, comparability, comprehensibility and regional adaptation are essential qualities of policy-relevant erosion maps

Eső hatása a Csorsza-patak vízgyűjtőjének téli hidrológiai folyamataira

A vizsgálat 42 órája alatt (2016. február 3–4.) és az előtte lévő öt hónapban összesen négy nagyobb mennyiségű csapadékesemény történt a Csorsza-patak vízgyűjtő területén. A vizsgált esőzés időszakában 21,6 mm csapadékmennyiség hullott összesen a vízgyűjtő területére 5 órás intervallumban. A csapadékesemény első órájában a patak zavarosság értéke majdnem megduplázódott, viszont így is viszonylag alacsony szinten maradt a későbbiekben mért értékekhez viszonyítva. Az esőzés kezdetét követő 7. órában emelkedett meg jelentősen a zavarosság mértéke, több mint 14-szeresére, a 13–14. órában pedig 34-szeresére nőtt a vizsgálat előtti naphoz viszonyítva. A Csorsza-patak zavarosságának nagysága nem sokkal a tetőzést követően nagy mértékben lecsökkent, 13 órával később pedig hasonló értékeket mutatott, mint a vizsgálat előtti esőzés nélküli időszakban. A nagyobb esőzések alkalmával az alacsonyabb területeken fekvő, minimális lejtésű szántó esetében telítettséghez közeli talajnedvesség-tartalom volt megfigyelhető, míg a legkisebb talajnedvesség-tartalom ingadozás az esőzést követően a gyepes és az erdős területekre volt jellemző. A jelen vizsgálatban összegyűjtött adatok alapján a Csorsza-patakból a Balatonba bekerülő talajhordalék mennyisége a téli időszakban, az erozív esőzések gyakoriságának ismeretében könnyebben és pontosabban becsülhető. Annak érdekében, hogy az éves átlag lebegtetett hordalék mennyiségének a becslését pontosabban el tudjuk végezni, több időszakos mérésre volna szükség. Munkánkat az OTKA K—101065 projekt, az OTKA PD—116157 és OTKA PD—116084 kutatási projekt, valamint a Bolyai János Kutatási Ösztöndíj támogatta. Külön köszönet Mózes Mariann és Bányász Ágnes részére a laboratóriumi vizsgálatokban nyújtott segítségükért, valamint Szegvári Győző és kollégáinak a zánkai vízminták gyűjtésében való hatalmas segítségükért. | The amount of suspended sediments leaving the Csorsza catchment area over time was investigated on the basis of turbidity measurements. These were taken at a distance of approximately 3.4 km from the vegetative study sites daily until the start of the erosive rain event, and every one or two hours during and after the event for a total of 42 hours. Soil water contents and soil temperatures were continuously measured at three depths (15, 40 and 70 cm below the surface), while overall weather data were obtained either from local measurements at the sites (for precipitation) or from meteorological stations close to the pilot area (for other meteorological variables). During an erosive rainfall event (precipitation = 21.6 mm; 3 Feb. 2016), a rain gauge was placed at the study site to measure precipitation intensities. During the 3-hour heavy rain event, precipitation rates of 5, 6 and 6 mm/h were recorded. Water turbidity measurements showed a good correlation with the amount of precipitation. During the erosive precipitation event, water turbidity increased considerably to approximately 6 times the background value (from 30–70 FNU to 300 FNU, where FNU stand for Formazin Nephelometric Unit) within two hours of the rain event. The greatest turbidity (~900 FNU) was measured 6 hours after the initial spike; but 5 hours after the peak the measured turbidity values were already similar to values prior to the precipitation event