A Model for Continental-Scale Water Erosion and Sediment Transport and Its Application to the Yellow River Basin

Quantifying suspended sediment discharge at large catchment scales has significant implications for various research fields such as water quality, global carbon and nutrient cycle, agriculture sustainability, and landscape evolution. There is growing evidence that climate warming is accelerating the water cycle, leading to changes in precipitation and runoff and increasing the frequency and intensity of extreme weather events, which could lead to intensive erosion and sediment discharge. However, suspended sediment discharge is still rarely represented in regional climate models because it depends not only on the sediment transport capacity based on streamflow characteristics but also on the sediment availability in the upstream basin. This thesis introduces a continental-scale Atmospheric and Hydrological-Sediment Modelling System (AHMS-SED), which overcomes the limitations of previous large-scale water erosion models. Specifically, AHMS-SED includes a complete representation of key hydrological, erosion and sediment transport processes such as runoff and sediment generation, flow and sediment routing, sediment deposition, gully erosion and river irrigation. In this thesis, we focus on developing and applying AHMS-SED in the Yellow River Basin of China, an arid and semi-arid region known for its wide distribution of loess and the highest soil erosion rate in the world. There are three key issues involving the model development and application: human perturbation (irrigation) of the water cycle, the uncertainty of precipitation forcing on the water discharge and the large-scale water erosion and sediment transport. This thesis addresses all these three issues in the following way. First, a new irrigation module is integrated into the Atmospheric and Hydrological Modelling System (AHMS). The model is calibrated and validated using in-situ and remote sensing observations. By incorporating the irrigation module into the simulation, a more realistic hydrological response was obtained near the outlet of the Yellow River Basin. Second, an evaluation of six precipitation-reanalysis products is performed based on observed precipitation and model-simulated river discharge by the AHMS for the Yellow River Basin. The hydrological model is driven with each of the precipitation-reanalysis products in two ways, one with the rainfall-runoff parameters recalibrated and the other without. Our analysis contributes to better quantifying the reliability of hydrological simulations and the improvement of future precipitation-reanalysis products. Third, a regional-scale water erosion and sediment transport model, referred to as AHMS-SED, is developed and applied to predicting continental-scale fluvial transport in the Yellow River Basin. This model couples the AHMS with the CASCade 2-Dimensional SEDiment (CASC2D-SED) and takes into account gully erosion, a process that strongly affects the sediment supply in the Chinese Loess Plateau. The AHMS-SED is then applied to simulate water erosion and sediment processes in the Yellow River Basin for a period of eight years, from 1979 to 1987. Overall, the results demonstrate the good performance of the AHMS-SED and the upland sediment discharge equation based on rainfall erosivity and gully area index. AHMS-SED is also used to predict the evolution of sediment transport in the Yellow River Basin under specific climate change scenarios. The model results indicate that changes in precipitation will have a significant impact on sediment discharge, while increased irrigation will reduce the sediment discharge from the Yellow River

The Effect of Hydrology on Soil Erosion

This Special Issue includes manuscripts about soil erosion and degradation processes and the accelerated rates due to hydrological processes and climate change. The new research included in this issue focuses on measurements, modeling, and experiments in field or laboratory conditions developed at different scales (pedon, hillslope, and catchment). This Special Issue received investigations from different parts of the world such as Ethiopia, Morocco, China, Iran, Italy, Portugal, Greece, and Spain, among others. We are happy to see that all papers presented findings characterized as unconventional, provocative, innovative, and methodologically new. We hope that the readers of the journal Water can enjoy and learn about hydrology and soil erosion using the published material, and share the results with the scientific community, policymakers, and stakeholders to continue this amazing adventure, facing plenty of issues and challenges

Soil-Water Conservation, Erosion, and Landslide

The predicted climate change is likely to cause extreme storm events and, subsequently, catastrophic disasters, including soil erosion, debris and landslide formation, loss of life, etc. In the decade from 1976, natural disasters affected less than a billion lives. These numbers have surged in the last decade alone. It is said that natural disasters have affected over 3 billion lives, killed on average 750,000 people, and cost more than 600 billion US dollars. Of these numbers, a greater proportion are due to sediment-related disasters, and these numbers are an indication of the amount of work still to be done in the field of soil erosion, conservation, and landslides. Scientists, engineers, and planners are all under immense pressure to develop and improve existing scientific tools to model erosion and landslides and, in the process, better conserve the soil. Therefore, the purpose of this Special Issue is to improve our knowledge on the processes and mechanics of soil erosion and landslides. In turn, these will be crucial in developing the right tools and models for soil and water conservation, disaster mitigation, and early warning systems

Infiltration and surface runoff dynamics on dryland hillslopes: a new method

Drylands cover approximately 41% of the Earth’s land surface (Middleton and Thomas, 1997); a habitat for over 38% of the planet's population (Huang et al., 2017). Understanding the interaction between ground surface characteristics, infiltration and overland flow in this environment is paramount to identifying areas vulnerable to erosion and flash flooding. Currently, infiltration is measured in drylands using techniques which are often not suited to the environment. Existing measurement methods typically cannot be used on steep slopes, and slopes with stone or vegetation cover, without disturbing the natural soil. As well as this, the impact of overland flow is often neglected from measurements. Here, a new method for quantifying infiltration and overland flow is presented: ‘the infiltrator’. The device outputs a pulse of water to the surface, allowing the measurement of runoff dimensions. Soil surface and slope characteristics are also measured with the use of field and GIS based techniques. The methods enable two main research questions to be assessed: (i) the impact of surface cover on surface runoff, and (ii) the influence of surface characteristics on flow concentration. The infiltrator was used successfully on rangeland slopes in a semi-arid environment (Salema, Western Algarve, Portugal), allowing for assessment of infiltration and overland flow, without disturbing the natural soil. Using regression modelling, the results from experimentation using the infiltrator indicted that: (i) infiltration and the nature of surface runoff are strongly related to stone and vegetation cover, and (ii) flow concentration controls include those identified in (i), as well as surface roughness and slope angle. The new method effectively enables the quantification of infiltration and overland flow, whilst remaining representative of the surface. It can be used on slopes up to 40°, and is an inexpensive, quick solution to characterising the vulnerability of dryland slopes to surface runoff and erosion

Afforestation and Reforestation: Drivers, Dynamics, and Impacts

Afforestation/reforestation (or forestation) has been implemented worldwide as an effective measure towards sustainable ecosystem services and addresses global environmental problems such as climate change. The conversion of grasslands, croplands, shrublands, or bare lands to forests can dramatically alter forest water, energy, and carbon cycles and, thus, ecosystem services (e.g., carbon sequestration, soil erosion control, and water quality improvement). Large-scale afforestation/reforestation is typically driven by policies and, in turn, can also have substantial socioeconomic impacts. To enable success, forestation endeavors require novel approaches that involve a series of complex processes and interdisciplinary sciences. For example, exotic or fast-growing tree species are often used to improve soil conditions of degraded lands or maximize productivity, and it often takes a long time to understand and quantify the consequences of such practices at watershed or regional scales. Maintaining the sustainability of man-made forests is becoming increasingly challenging under a changing environment and disturbance regime changes such as wildland fires, urbanization, drought, air pollution, climate change, and socioeconomic change. Therefore, this Special Issue focuses on case studies of the drivers, dynamics, and impacts of afforestation/reforestation at regional, national, or global scales. These new studies provide an update on the scientific advances related to forestation. This information is urgently needed by land managers and policy makers to better manage forest resources in today’s rapidly changing environments

A mathematical model development for simulating in-stream processes of non-point source pollutants.

Doctoral Degree. University of KwaZulu-Natal, Durban.In coming years, chronic water stress is inevitable owing to the unavailability of fresh water. This situation is occasioned by rapid urbanisation, climate change, rising food demand, and production. The increasing rate of water scarcity associated with water pollution problems, makes water quality management an issue of great concern. Rivers owe their existence to the relationship of rainfalls, soil properties and land use within a catchment. The entire hydrological processes that occur in the catchment area has a direct effect on occurrences and quality of the rivers there-in. A principal part of the hydrological cycle is runoff generation. Runoff characterises soil erosion, sediment transport, pollutants and chemicals all otherwise referred to as non-point source pollutants and released into water bodies. Most non-point source pollutants are generated from agricultural fields, informal settlements, mining fields, industrial areas, and roads. These sources produce increased nutrient concentrates (sewage effluent from informal settlements and fertilisers from agricultural fields) and toxic substances which alter the water quality in uncertain quantities. This affects aquatic biota and ultimately human health negatively. Non-point source pollution is a major source of water quality degradation globally and is the single most significant threat to subsurface and surface sources of usable water. Developed countries, unlike many developing countries, have long sought ways to stop the release of non-point source pollution directly into natural rivers through the establishment of best management practices but unfortunately with little success in actual practice. Numerous non-point source models exist which are basically watershed based and are limited to simulate the in-stream processes of non-point source pollution in water channels. Most existing non-point source models are site-specific, cumbersome to manipulate, need high-level operational skills and extensive data sets. Consequently, these models are difficult to use in areas apart from where they were developed and with limited data sets, as is the case with developing countries. Hence, to develop a non-point source pollution model that would adequately and effectively, simulate non-point source pollution in water bodies, towards restoring good river health is needed. This is required to enhance the proper monitoring and remediation of water sources affected by Non-Point Source Pollution especially in areas that have scarce data. Using the concept of the Hybrid Cells in Series model in this study, a hydrodynamic riverine Non-point source pollution model is conceptualized to simulate conservative pollutants in natural rivers. The Hybrid Cells in Series model was conceptualized to address the limitations identified in the classical advection dispersion model which is the foundation for all water quality modelling. The proposed model is a three-parameter model made up of three zones, which describes pure advection through time delay in a plug zone, and advection and dispersion occurring in two other thoroughly mixed zones linked in sequence. The model considers lateral inflow and pollutant loading along the river reach in addition to the point source pollutant entry and flow from upstream stations. The model equation for water quality along with hydrodynamic equation has been solved analytically using Laplace Transform. The derived mathematical formulation is appropriately coded, using FORTRAN programming language. Other components such as hyporheic exchange process and first order kinetic reaction simulations are incorporated to the proposed model. The response of these models matches the numerical solution of the classical Advection Dispersion Equation model satisfactorily when compared. The potential of the proposed model is tested using field data obtained from verifiable existing literature. A performance evaluation at 95 percent confidence is carried out. The correlation results of the observed and simulated data are seen to be in good agreement. The breakthrough curves obtained from the proposed model shows its capability to simulate Non-point source pollution transport in natural rivers effectively. The simplicity of the Hybrid Cells in Series model makes it a viable model for simulating contaminant transport from non-point sources. As the model has been validated using recorded data collected from the field for a specific tracer injection event, it is imperative to carry out investigation on changes in model parameters before, during and after storm events. However, this study adequately addressed and attempted to develop, validate new model components for simulating non-point source pollutant transport processes in stream

Forest Management and Water Resources in the Anthropocene

Decades of research has provided a depth of understanding on the relationships among forests and water, and how these relationships change in response to climate variability, disturbance, and forest management. This understanding has facilitated a strong predictive capacity and the development of best management practices to protect water resources with active management. Despite this understanding, the rapid pace of changes in climate, disturbance regimes, invasive species, human population growth, and land use expected in the 21st century is likely to create substantial challenges for watershed management that may require new approaches, models, and best management practices. These challenges are likely to be complex and large scale, involving a combination of direct effects and indirect biophysical watershed responses, as well as socioeconomic impacts and feedbacks. We explore the complex relationships between forests and water in a rapidly changing environment, examine the trade-offs and conflicts between water and other resources, and examine new management approaches for sustaining water resources in the future

Advancing understanding of development policy impacts on transboundary river basins: Integrated watershed modelling of the Lower Mekong Basin.

The management of transboundary river basins across developing countries, such as the Lower Mekong River Basin (LMB), is frequently challenging given the development and conservation divergences of the basin countries. Driven by needs to sustain economic performance and reduce poverty, the LMB countries are embarking on significant land use changes in the form hydropower dams, to fulfill their energy requirements. This pathway could lead to irreversible changes to the ecosystem of the Mekong River, if not properly managed. This thesis aims to explore the potential effects of changes in land use —with a focus on current and projected hydropower operations— on the Lower Mekong River network streamflow and instream water quality. To achieve this aim, this thesis first examined the relationships between the basin land use/land cover attributes, and streamflow and instream water quality dynamics of the Mekong River, using total suspended solids and nitrate as proxies for water quality. Findings from this allowed framing challenges of integrated water management of transboundary river basins. These were used as criteria for selecting eWater’s Source modelling framework as a management tool that can support decision-making in the socio-ecological context of the LMB. Against a combination of predictive performance metrics and hydrologic signatures, the model’s application in the LMB was found to robustly simulate streamflow, TSS and nitrate time series. The model was then used for analysing four plausible future hydropower development scenarios, under extreme climate conditions and operational alternatives. This revealed that hydropower operations on either tributary or mainstream could result in annual and wet season flow reduction while increasing dry season flows compared to a baseline scenario. Conversely, hydropower operation on both tributary and mainstream could result in dry season flow reduction. Both instream TSS and nitrate loads were predicted to reduce under all three scenarios compared to the baseline. These effects were found to magnify under extreme climate conditions, but were less severe under improved operational alternatives. In the LMB where hydropower development is inevitable, findings from this thesis provide an enhanced understanding on the importance of operational alternatives as an effective transboundary cooperation and management pathway for balancing electricity generation and protection of riverine ecology, water and food security, and people livelihoods

Modelling weed management effects on soil erosion in rubber plantations in Southwest China

Land use in Xishuangbanna, Southwest China, a typical subtropical rain forest region, has been dramatically changed over the past 30 years. Driven by favorable market opportunities, a rapid expansion of rubber plantations has taken place. This disturbs forests and land occupied by traditional swidden agriculture thus strongly affecting hydrological/erosion processes, and threatening soil fertility and water quality. The presented PhD thesis aimed at assessing farmer acceptable soil conservation strategies in rubber plantations that efficiently control on-site soil loss over an entire rotation time (25 40 years) and off-site sediment yield in the watershed. The study started with field investigations on erosion processes and soil conservation management options in rubber plantations (Chapter 2 and 3). Based on the field data, the physically based model Land Use Change Impact Assessment (LUCIA) was employed to assess long-term conservation effects in rubber plantations (Chapter 4) and scale effects on sediment yield in the watershed (Chapter 5). Specifically, the first study aimed at assessing soil loss in rubber plantations of different ages (4, 12, 18, 25 and 36 year old) and relating erosion potential to surface cover and fine root density by applying the Universal Soil Loss Equation (USLE) model. This study adopted the space-for-time substitution for field experimental design instead of establishing a long-term observation. Spatial heterogeneity of soil properties (e.g. texture, organic carbon content) and topography (slope steepness and length) interfered erosion at different plantation ages. To meet this challenge, namely account for possible impacts of soil properties and slope on erosion, the empirical USLE model was applied in data analysis to calculate the combined annual cover, management and support practice factor CP, which represents ecosystem erosivity. Calculated CP values varied with the growth phase of rubber in the range of 0.006 - 0.03. Surface cover was recognized as the major driver responsible for the erosive potential changes in rubber plantations. The mid-age rubber plantation exhibited the largest erosion (3 Mg ha-1) due to relatively low surface cover (40%-60%) during the rainy season, which was attributed to low weed cover (below 20%) and the low surface-litter cover favored by a high decomposition rate. Based on the results of the first study, the second study focused on reducing soil loss in rubber plantations by maintaining a high surface cover through improved weed management. Among the different weeding strategies tested, no-weeding most efficiently reduced on-site soil loss to 0.5 Mg ha-1. However, due to the low farmer acceptance of the no-weeding option, we recommend reducing herbicide application to a single dose at the beginning of the rainy season (once-weeding) to better conserve soil as well as inhibiting overgrowth of the understory vegetation. As the second experiment lasted only one-year, while rubber plantation is a perennial crop with a commercial lifespan of 25 40 years, the third study applied the LUCIA model to simulate the temporal dynamics of soil erosion in rubber plantations under different weeding strategies. The erosion module in LUCIA was extended to simulate both runoff and rainfall based soil detachment to better reflect the impact of the multi-layer structure of the plantation canopy. The improved LUCIA model successfully represented weed management effects on soil loss and runoff at the test site with a modelling efficiency (EF) of 0.5-0.96 and R2 of 0.64-0.92. Long-term simulation results confirmed that once-weeding controlled annual soil loss below 1 Mg ha-1 and kept weed cover below 50%. Therefore, this weeding strategy was suggested as an eco- and farmer friendly management in rubber plantations. Furthermore, LUCIA was applied at watershed level to evaluate plot conservation impact on sediment yield. Two neighboring sub-watersheds with different land cover were chosen: one a forest dominated (S1, control), the other with a mosaic land use (S2), which served to assess mono-conservation (conservation only in rubber plantations) and multi-conservation (conservation in maize, rubber and tea plantations) effects on total sediment yields. The model was well calibrated and validated based on peak flow (EF of 0.70 for calibration and 0.83 for validation) and sediment yield (EF of 0.71 for calibration and 0.95 for validation) measured from the two watersheds outlet points. Model results showed that improved weed management in rubber plantations can efficiently reduce the total sediment yields by 20%; while multi-conservation was largely able to offset increased sediment yields by land use change. In summary, while exploring the dynamics of erosion processes in rubber plantations, a physically based model (LUCIA) was extended and applied to simulate weed management effects over an entire crop cycle (40 years) and implications at higher scale level (watershed sediment yield). Once-weeding per year was identified as an improved management to reduce on-site erosion and off-site sediment yield. But to fully offset increased sediment yield by land use change, a multi-conservation strategy should be employed, which not only focuses on new land uses, like rubber plantations, but also takes care of traditional agricultural types. A conceptual framework is proposed to further assess the specific sub-watershed erosion (e.g. sediment or water yield) effects in large watersheds by spatially combining process-oriented and data-driven (e.g. statistic based, machine learning based) models. This study also serves as a case study to investigate ecological issues (e.g. erosion processes, land use change impact) based on short-term data and modelling in the absence of long-term observations.Die Landnutzung in Xishuangbanna, Südwestchina, einer typischen subtropischen Regenwaldregion, hat sich in den letzten 30 Jahren dramatisch verändert. Getrieben von günstigen Marktchancen hat ein rapider Ausbau von Kautschukplantagen stattgefunden. Dies beeinflusst Wälder und Flächen, die durch traditionellem Brandrodungsackerbau bewirtschaftet werden, was starke Auswirkungen auf hydrologische Prozesse und Erosionsprozesse hat und die Bodenfruchtbarkeit und Wasserqualität bedroht. Die vorliegende Dissertation zielte auf die Bewertung von akzeptablen Bodenschutzstrategien für Landwirte in Kautschukplantagen ab, die den Bodenverlust innerhalb des Standortes während einer ganzen Rotationszeit (25 - 40 Jahre) und den Sedimentausstoß außerhalb des Standortes im Wassereinzugsgebiet effizient kontrollieren. Die Studie begann mit Felduntersuchungen zu Erosionsprozessen und Bodenschutz-Managementoptionen in Kautschukplantagen (Kapitel 2 und 3). Basierend auf den Felddaten wurde das physikalisch basierte Modell "Land Use Change Impact Assessment" (LUCIA) eingesetzt, um Langzeitschutzeffekte in Kautschukplantagen (Kapitel 4) und Skaleffekte auf den Sedimentausstoß im Wassereinzugsgebiet zu bewerten (Kapitel 5). Konkret zielte die erste Studie darauf ab, den Bodenverlust in Kautschukplantagen unterschiedlichen Alters (4, 12, 18, 25 und 36 Jahre alt) zu untersuchen und das Erosionspotenzial mit der Allgemeinen Bodenabtragsgleichung (USLE) in Beziehung zur Oberflächenbedeckung und Feinwurzeldichte zu setzen. In dieser Studie wurde die space-for-time substitution für experimentelle Feldforschung anstelle einer Langzeitbeobachtung übernommen. Räumliche Heterogenität der Bodeneigenschaften (z. B. Textur, organischer Kohlenstoffgehalt) und Topographie (Neigungssteilheit und -länge) beeinträchtigten die Erosion bei verschiedenen Pflanzungsaltern. Um dieser Herausforderung zu begegnen, nämlich mögliche Auswirkungen von Bodeneigenschaften und Gefälle auf die Erosion zu berücksichtigen, wurde das empirische USLE-Modell in der Datenanalyse, zur Berechnung der kombinierten jährlichen Bodenbedeckung, Management und support practice factor (CP), das die Ökosystem-Erosivität darstellt, verwendet. Berechnete CP-Werte variierten mit der Wachstumsphase von Kautschuk im Bereich von 0,006-0,03. Die Oberflächenbedeckung wurde als der Haupttreiber für Änderungen des erosiven Potentials in Kautschukplantagen anerkannt. Die Kautschukplantage mittleren Alters wies aufgrund der relativ geringen Oberflächenbedeckung (40% -60%) während der Regenzeit die größte Erosion (3 Mg ha-1) auf. Dies wurde auf einen geringen Unkrautbewuchs (unter 20%) und eine geringe Bodenbedeckung durch Oberflächenstreu, verursacht durch eine hohe Zersetzungsrate, zurückgeführt. Basierend auf den Ergebnissen der ersten Studie konzentrierte sich die zweite Studie auf die Verringerung des Bodenverlusts in Kautschukplantagen, indem eine hohe Oberflächenbedeckung durch verbessertes Unkrautmanagement aufrechterhalten wurde. Unter den verschiedenen getesteten Unkrautbekämpfungsstrategien reduzierte no-weeding den Bodenverlust vor Ort auf 0,5 Mg ha-1 am effizientesten. Aufgrund der geringen Akzeptanz der Unkrautbekämpfung durch den Landwirt empfehlen wir jedoch zu Beginn der Regenzeit (einmaliges Unkrautjäten) eine Herbizidapplikation auf eine Einzeldosis zu reduzieren, um den Boden besser zu erhalten und das Überwachsen der Unterholzvegetation zu verhindern. Da das zweite Experiment nur ein Jahr dauerte, während die Kautschukplantage eine mehrjährige Pflanze mit einer kommerziellen Lebensdauer von 25 bis 40 Jahren ist, wurde in der dritten Studie das LUCIA-Modell zur Simulation der zeitlichen Dynamik der Bodenerosion in Kautschukplantagen unter verschiedenen Strategien eingesetzt. Das Erosionsmodul in LUCIA wurde erweitert, um sowohl oberflächenabfluss- als auch niederschlagsbedingte Bodenerosion zu simulieren, um den Einfluss der mehrschichtigen Struktur des Plantagenschirms besser widerzuspiegeln. Das verbesserte LUCIA-Modell stellte erfolgreich die Auswirkungen des Unkrautmanagements auf den Bodenverlust und den Oberflächenabfluss am Versuchsstandort mit einer Modellierungseffizienz (EF) von 0,5-0,96 und R2 von 0,64-0,92 dar. Die Ergebnisse der Langzeitsimulationen bestätigten, dass "einmaliges Jäten" den jährlichen Bodenverlust unter 1 Mg ha-1 kontrollierte und die Unkrautabdeckung unter 50% hielt. Daher wurde diese Unkrautbekämpfungsstrategie als umwelt- und landwirtfreundliches Management in Kautschukplantagen vorgeschlagen. Darüber hinaus wurde LUCIA auf Wassereinzugsgebietsebene angewendet, um die Auswirkung der Flächenerhaltung auf den Sedimentausstoß zu bewerten. Zur Bewertung der Auswirkungen auf die Gesamtsedimentmengen wurden zwei benachbarte Teileinzugsgebiete mit unterschiedlicher Landbedeckung ausgewählt. Für die Auswirkungen von Einzelschutz (mono-conservation; Schutz nur in Kautschukplantagen) hat eine von Wald dominierende Landnutzung (S1, Kontrolle) gedient und für die Auswirkungen von Mehrfachschutz (multi-conservation; Schutz in Mais-, Kautschuk- und Teeplantagen) eine Mosaiklandnutzung (S2). Das Modell wurde gut kalibriert und validiert basierend auf dem Peak-Flow (EF von 0,70 für die Kalibrierung und 0,83 für die Validierung) und dem Sedimentertrag (EF von 0,71 für die Kalibrierung und 0,95 für die Validierung), die an den zwei Austrittsstellen des Wassereinzugsgebiets gemessen wurden. Die Modellergebnisse zeigten, dass ein verbessertes Unkrautmanagement in Kautschukplantagen die gesamten Sedimentausbeuten um 20% reduzieren kann; während Mehrfachschutz weitgehend in der Lage war, erhöhte Sedimenterträge durch Landnutzungsänderungen auszugleichen. Zusammenfassend wurde, während der Untersuchung der Dynamik von Erosionsprozessen in Kautschukplantagen, ein physikalisch basiertes Modell (LUCIA) erweitert und angewendet, um Unkrautmanagementeffekte über einen gesamten Erntezyklus (40 Jahre) und Implikationen auf höherer Maßstabsebene (Wasserscheidensedimentmenge) zu simulieren. Einmaliges Unkrautbekämpfung pro Jahr wurde als verbessertes Management identifiziert, um die Erosion vor Ort und den Sedimentaustrag außerhalb des Wassereinzugsgebietes zu reduzieren. Um den durch die Landnutzungsänderung erhöhten Sedimentausstoß jedoch vollständig ausgleichen zu können, sollte eine Mehrfachschutzstrategie angewandt werden, die sich nicht nur auf neue Landnutzungen wie Kautschukplantagen konzentriert, sondern sich auch um traditionelle landwirtschaftliche Typen kümmert. Ein konzeptueller Rahmen wird vorgeschlagen, um die spezifischen Erosionseffekte der sub-Wassereinzugsgebiete (z. B. Sediment oder Wasserausbeute) in großen Wassereinzugsgebieten durch räumliche Kombination von prozessorientierten und datengesteuerten (z. B. statistisch und machine-learning basierten) Modellen weiter zu bewerten. Diese Studie dient auch als Fallstudie zur Untersuchung ökologischer Fragen (z. B. Erosionsprozesse, Auswirkungen von Landnutzungsänderungen) auf der Grundlage von Kurzzeitdaten und Modellierung in Abwesenheit von Langzeitbeobachtungen