Evaluating land cover change and its impact on hydrological regime in Upper Shire River Catchment, Malawi

A study was conducted to investigate hydrological impacts of land cover changes in the degradation of the hydrological on flow regimes of the Upper Shire river, Malawi. Remote sensing techniques were used to inventory temporal changes of land cover changes in the catchment. Hydrological data were analyzed to reveal the alterations ecosystems, and water resources for an informed decision on proper catchment planning and management and trends for two periods; 1989 and 2002. The study revealed significant changes in magnitude and direction that have occurred in the catchment between 1989 and 2002, mainly in areas of human habitation. Trends in land cover change in the Upper Shire river catchment depict land cover transition from woodlands to mostly cultivated/ grazing and built-up areas. The land cover mapping showed that 23% of the land was covered by agricultural land in 1989. Subsistence agricultural area has increased by 18%, occupying 41% of the study area in 2002. The effects of the derived land cover changes on river flow in the Upper Shire river were investigated using the semi distributed soil and water assessment tool (SWAT) model. River flows were found to be highly variable and sensitive to land cover changes. Simulation results show that 2002 land cover data produces higher flow peaks and faster travel times compared to the 1989 land cover data. The changes detected indicate the effects of land use pressure in the catchment. The study highlights the importance of considering effects of land use and land cover changes on ecosystems, and water resources for an informed decision on proper catchment planning and management

Proportional Variation of Potential Groundwater Recharge as a Result of Climate Change and Land-Use: A Study Case in Mexico

Artículo en revista indexadaThis work proposes a methodology whereby the selection of hydrologic and land-use cover change (LUCC) models allows an assessment of the proportional variation in potential groundwater recharge (PGR) due to both land-use cover change (LUCC) and some climate change scenarios for 2050. The simulation of PGR was made through a distributed model, based on empirical methods and the forecasting of LUCC stemming from a supervised classification with remote sensing techniques, both inside a Geographic Information System. Once the supervised classification was made, a Markov-based model was developed to predict LUCC to 2050. The method was applied in Acapulco, an important tourism center for Mexico. From 1986 to 2017, the urban area increased 5%, and by 2050 was predicted to cover 16%. In this period, a loss of 7 million m3 of PGR was assumed to be caused by the estimated LUCC. From 2017 to 2050, this loss is expected to increase between 73 and 273 million m3 depending on the considered climate change scenario, which is the equivalent amount necessary for satisfying the water needs of 6 million inhabitants. Therefore, modeling the variation in groundwater recharge can be an important tool for identifying water vulnerability, through both climate and land-use change.CONACyT Centro de Ciencias de Desarrollo Regional (CCDR

Assessing the Role of Climate Change and Land Cover Change in Eco-Hydrologic Modeling (Snowmelt Timing and Dissolved Organic Carbon Fluxes)

This study explores temporal trends in snowmelt timing, dissolved organic carbon (DOC) concentrations, and DOC fluxes in the large forested Penobscot watershed of Maine. The spatially-distributed process-based Regional Hydro-Ecological Simulation System (RHESSys) model was used to simulate streamflows and DOC fluxes and concentrations from 2004-2013 with peak transport generally associated with snowmelt. Results were evaluated with field measurements (streamflow, DOC concentrations and fluxes) and remotely sensed products (Net Primary Production (NPP) and Leaf Area Index (LAI)). The annual and inter annual variability in the amount of fluvial DOC export was further explored under future climate change scenarios and predicted land cover compositions of the watershed

Modelling the Effects of Changes in Forest Cover and Climate on Hydrology of Headwater Catchments in South-Central Chile

This study analyses the changes in the runoff of forested experimental catchments in south-central Chile, to determine to what extent observed trends can be attributed to effects of intensive forestry and/or climate change. For this, we applied the distributed TETIS® model to eight catchments (7.1−413.6 ha) representative of the land uses and forestry activities in this geographical area. Rainfall and runoff data collected between 2008 and 2015 were used for modelling calibration and validation. Simulation of three land uses (current cover, partial harvest and native forest) and 25 combinations of climatic scenarios (percentage increases or decreases of up to 20% of rainfall and evapotranspiration relative to the no-change scenario applied to input series) were used in each calibration. We found that changes in land use and climate had contrasting effects on runoff. Smaller catchments affected by the driest climatic scenarios experienced higher runoff when the forest cover was lower than under full forest cover (plantations or native forests). In contrast, larger catchments under all climatic scenarios yielded higher runoff below the full forest cover than under partial harvest and native forest. This suggests that runoff can be influenced, to a great extent, by rainfall decrease and evapotranspiration increase, with the model predicting up to a 60% decrease in runoff yield for the dry’s climatic scenario. This study proves to be relevant to inform ongoing discussions related to forest management in Chile, and is intended to minimize the impact of forest cover on runoff yield under uncertain climatic scenarios.The authors acknowledge the support from the Economy and Knowledge Department of the Catalan Government through the Consolidated Research Group ‘Fluvial Dynamics Research Group’—RIUS (2017 SGR 459)

Evaluating land-cover change effects on runoff and recharge in Kawela, Moloka'i, Hawai'i

M.S. University of Hawaii at Manoa 2013.Includes bibliographical references.The Precipitation Runoff Modeling System (PRMS), a modular, physically based, distributed-parameter modeling system, was used to develop a watershed model for Kawela, Moloka‘i to evaluate the impact of changing watershed characteristics on surface-water runoff and groundwater recharge. Available spatial information was processed in a geographic information system (GIS) environment and assigned to the delineated hydrologic response units (HRUs) within the watershed. PRMS simulates different parts of the hydrological cycle based on a set of user-defined modules, and each component of the hydrological cycle is computed by empirical relations or process algorithms. For each HRU, an energy and a water balance is computed; the sum of all of the HRU’s water-budget components produces the watershed’s total hydrological response. The model was manually calibrated using a climatic adjustment coefficient and this calibration resulted in a reasonable match between simulated and observed hydrographs and flow volumes. To further minimize any differences between the simulated and observed streamflow values, the model was automatically calibrated using PEST (Parameter ESTimation) software. The simulated total runoff volume was within 8.7 percent over the entire simulation period (04/01/2006-03/31/2010). Simulation results for the four-year period indicate that 91 percent of the precipitation that falls on the watershed is partitioned into evapotranspiration (43 percent) and groundwater recharge (48 percent). A much smaller percentage of rainfall is partitioned into runoff (8 percent) that is measured at the outlet of the watershed. The calibrated model was used to assess different watershed restoration and degradation scenarios and evaluate the hydrological system’s sensitivity to changes in land cover. Compared to the current land cover, the tested land-cover change scenario of vegetation denudation resulted in a smaller component of fog-drip, which translated to a 4 percent decrease in precipitation and consequently only a 1 percent increase in the amount of precipitation partitioned into runoff. However, vegetation restoration decreases runoff by 16 percent, which, by inference, would lead to reduced sediment loading of the nearshore environment. The amount of precipitation partitioned into recharge changed by less than 5 percent in both scenarios. PRMS is a helpful management tool that can be used to evaluate changes in runoff and recharge under different land-cover change scenarios

Soil Erosion and Sustainable Land Management (SLM)

This Special Issue titled “Soil Erosion and Sustainable Land Management” presents 13 chapters organized into four main parts. The first part deals with assessment of soil erosion that covers historical sediment dating to understand past environmental impacts due to tillage; laboratory simulation to clarify the effect of soil surface microtopography; integrated field observation and the random forest machine learning algorithm to assess watershed-scale soil erosion assessment; and developing the sediment delivery distributed (SEDD) model for sub-watershed erosion risk prioritization. In Part II, the factors controlling soil erosion and vegetation degradation as influenced by topographic positions and climatic regions; long-term land use change; and improper implementation of land management measures are well dealt with. Part III presents different land management technologies that could reduce soil erosion at various spatial scales; improve land productivity of marginal lands with soil microbes; and reclaim degraded farmland using dredged reservoir sediments. The final part relates livelihood diversification to climate vulnerability as well as the coping strategy to the adverse impacts of soil erosion through sustainable land management implementation which opens prospects for policy formulation. The studies cover regions of Africa, Europe, North America and Asia, being dominantly conducted under the framework of international scientific collaborations through employing a range techniques and scales, from the laboratory to watershed scales. We believe those unique features of the book could attract the interest of the wider scientific community worldwide

Assessment of different modelling studies on the spatial hydrological processes in an arid alpine catchment

To assess the model description of spatial hydrological processes in the arid alpine catchment, SWAT and MIKE SHE were jointly applied in Yarkant River basin located in northwest China. Not only the simulated daily discharges at the outlet station but also spatiotemporal distributions of runoff, snowmelt and evapotranspiration were analyzed contrastively regarding modules' structure and algorithm. The simulation results suggested both models have their own strengths for particular hydrological processes. For the stream runoff simulation, the significant contributions of lateral interflow flow were only reflected in SWAT with a proportion of 41.4 %, while MIKE SHE simulated a more realistic distribution of base flow from groundwater with a proportion of 21.3 %. In snowmelt calculation, SWAT takes account of more available factors and got better correlations between snowmelt and runoff in temporal distribution, however, MIKE SHE presented clearer spatial distribution of snowpack because of fully distributed structure. In the aspect of water balance, less water was evaporated because of limitation of soil evaporation and less spatially distributed approach in SWAT, on another hand, the spatial distribution of actual evapotranspiration (ETa) in MIKE SHE clearly expressed influence of land use. Whether SWAT or MIKE SHE, without multiple calibrations, the model's limitation might bring in some biased opinions of hydrological processes in a catchment scale. The complementary study of combined results from multiple models could have a better understanding of overall hydrological processes in arid and scarce gauges alpine region

Accurate simulation of ice and snow runoff for the mountainous terrain of the Kunlun Mountains, China

While mountain runoff provides great potential for the development and life quality of downstream populations, it also frequently causes seasonal disasters. The accurate modeling of hydrological processes in mountainous areas, as well as the amount of meltwater from ice and snow, is of great significance for the local sustainable development, hydropower regulations, and disaster prevention. In this study, an improved model, the Soil Water Assessment Tool with added ice-melt module (SWATAI) was developed based on the Soil Water Assessment Tool (SWAT), a semi-distributed hydrological model, to simulate ice and snow runoff. A temperature condition used to determine precipitation types has been added in the SWATAI model, along with an elevation threshold and an accumulative daily temperature threshold for ice melt, making it more consistent with the runoff process of ice and snow. As a supplementary reference, the comparison between the normalized difference vegetation index (NDVI) and the quantity of meltwater were conducted to verify the simulation results and assess the impact of meltwater on the ecology. Through these modifications, the accuracy of the daily flow simulation results has been considerably improved, and the contribution rate of ice and snow melt to the river discharge calculated by the model increased by 18.73%. The simulation comparison of the flooding process revealed that the accuracy of the simulated peak flood value by the SWATAI was 77.65% higher than that of the SWAT, and the temporal accuracy was 82.93% higher. The correlation between the meltwater calculated by the SWATAI and the NDVI has also improved significantly. This improved model could simulate the flooding processes with high temporal resolution in alpine regions. The simulation results could provide technical support for economic benefits and reasonable reference for flood prevention