Simulation of sub-basin sediment yields and river runoffs into Davao Gulf, Philippines

2020 ◽  
Author(s):  
Adonis Gallentes ◽  
Peter Jeffrey Maloles ◽  
Cesar Villanoy
Keyword(s):  
Land Use ◽  
Sediment Yield ◽  
Land Surface ◽  
River Discharge ◽  
Marine Protected Area ◽  
Marine Ecosystem ◽  
The Philippines ◽  
Marine Biodiversity ◽  
Surface Erosion ◽  
Sediment Yields

<p>The Philippines is a country within the Coral Triangle which is known to be the center of the most biologically diverse marine ecosystem in the world. Despite being a crucial area for marine biodiversity, discharge measurements of many rivers in the country are either sparse or non-existent. Such data are important in assessing aspects such as sedimentation which is highly related to the health of the reef community.</p><p>Here, we applied SWAT hydrological model in order to simulate the sediment yield of sub-basins and river discharge surrounding Davao Gulf, one of the country’s richest zones in terms of fish production. Monthly-averaged results of the model from 2001 to 2018 indicate that the relative maxima of sediment yield coincide with precipitation maxima, and that consecutive rainfall events which start around midyear results to higher erodibility and thus, higher peaks in sediment yield during the second half of each year until the early part of the following year. Dependence of sediment yield on slope class/angle and land use was also observed, identifying the northwestern catchments as critical sources of land surface erosion. Good agreement was obtained between simulations of river discharge and the sparse observed streamflow values during model validation (Davao River: NSE=0.61, R<sup>2</sup>=0.61, PBIAS = 2.87, r= 0.78; Hijo River: NSE=0.62, R<sup>2</sup>=0.90, PBIAS = -2.1630, r= 0.95).</p><p>Overall, this modeling study helped fill in the temporal gaps of observed streamflow data from river gauges, and provided estimates of the historical streamflow pattern of those rivers with no river gauges. Outputs of this study can also be used as science-based reference in crafting laws and ordinances for proper land use and Marine Protected Area (MPA) management plans, with emphasized consideration of the likely effects of climate change such as the latitudinal shift of typhoon tracks, increasing temperature, and more pronounced precipitation events which have already been observed in the area during the past two decades. </p>

SWAT-based sediment yield simulation with mining land-use change scenario in Lanuza Bay, Philippines

2020 ◽  
Author(s):  
Peter Jeffrey Maloles ◽  
Adonis Gallentes ◽  
Cesar Villanoy
Keyword(s):  
Land Use ◽  
Sediment Yield ◽  
Assessment Tool ◽  
Marine Protected Area ◽  
Swat Model ◽  
Time Lag ◽  
The Philippines ◽  
Marine Biodiversity ◽  
Change Scenario ◽  
Mining Operations

<p>The Philippines is known for its rich marine biodiversity and is deemed as the apex of the world’s coral triangle. However, sediment yield studies and river discharge measurements in the country are sparse if not non-existent. High sediment rates have detrimental effects on water quality and consequently to coral reef health and marine biodiversity. Thus, modeling of runoff and sediment yield at a watershed level is important in assessing coral community environments.</p><p>In this study, a Soil and Water Assessment Tool (SWAT) based sediment yield simulation was done for Lanuza Bay-- a site with high productivity but increasing mining activity. Two simulations were conducted. The first utilized a land-use map before January 2011 and was made to run from January 1998 to August 2018 in order to simulate a scenario in which mining operations did not occur in the area. The second simulation utilized an updated land-use map that incorporated mining sites from January 2011 to August 2018.</p><p>SWAT model results indicate that slope class was the primary determinant of erosion rates (slope band > 20%). The study suggests that consecutive precipitation occurrences affected soil erodability and induced a time lag between precipitation and sediment yield peaks. The highest contributors to sediment yield at a sub-basin level were identified to be areas adjacent to or coinciding in mining or excavation sites. Comparing the scenarios with and without mining, mining contributed to 4% of the increase in the watershed’s total annual sediment yield.</p><p>Qualitative and historical validation shows reasonable agreement between simulated values and satellite images. The output of this study can be used as a science-based reference in crafting laws and policies for land-use management and Marine Protected Area (MPA) planning.</p>

CLIMATE- AND LAND USE-INDUCED RISKS TO WATERSHED SERVICES IN THE NYANDO RIVER BASIN, KENYA

2011 ◽  
Vol 47 (2) ◽  
pp. 339-356 ◽  
Author(s):  
MWANGI GATHENYA ◽  
HOSEA MWANGI ◽  
RICHARD COE ◽  
JOSEPH SANG
Keyword(s):  
Climate Change ◽  
Land Use ◽  
Land Use Change ◽  
Sediment Yield ◽  
Land Surface ◽  
Assessment Tool ◽  
Surface Condition ◽  
Water Yield ◽  
Minor Effect ◽  
Watershed Services

SUMMARYClimate change and land use change are two forces influencing the hydrology of watersheds and their ability to provide ecosystem services, such as clean and well-regulated streamflow and control of soil erosion and sediment yield. The Soil Water Assessment Tool, SWAT, a distributed, watershed-scale hydrological model was used with 18 scenarios of rainfall, temperature and infiltration capacity of land surface to investigate the spatial distribution of watershed services over the 3587 km2 Nyando basin in Western Kenya and how it is affected by these two forces. The total annual water yield varied over the 50 sub-basins from 35 to 600 mm while the annual sediment yield ranged from 0 to 104 tons ha−1. Temperature change had a relatively minor effect on streamflow and sediment yield compared to change in rainfall and land surface condition. Improvements in land surface condition that result in higher infiltration are an effective adaptation strategy to moderate the effects of climate change on supply of watershed services. Spatial heterogeneity in response to climate and land use change is large, and hence it is necessary to understand it if interventions to modify hydrology or adapt to climate change are to be effective.

scholarly journals Contrasting watershed-scale trends in runoff and sediment yield complicate rangeland water resources planning

2016 ◽  
Vol 20 (6) ◽  
pp. 2295-2307 ◽  
Author(s):  
Matthew D. Berg ◽  
Franco Marcantonio ◽  
Mead A. Allison ◽  
Jason McAlister ◽  
Bradford P. Wilcox ◽  
...  
Keyword(s):  
Sediment Yield ◽  
Land Surface ◽  
Sediment Cores ◽  
Watershed Scale ◽  
Landscape Changes ◽  
Sediment Yields ◽  
Dynamic Landscape ◽  
Cesium 137 ◽  
Lead 210 ◽  
Runoff And Sediment Yield

Abstract. Rangelands cover a large portion of the earth's land surface and are undergoing dramatic landscape changes. At the same time, these ecosystems face increasing expectations to meet growing water supply needs. To address major gaps in our understanding of rangeland hydrologic function, we investigated historical watershed-scale runoff and sediment yield in a dynamic landscape in central Texas, USA. We quantified the relationship between precipitation and runoff and analyzed reservoir sediment cores dated using cesium-137 and lead-210 radioisotopes. Local rainfall and streamflow showed no directional trend over a period of 85 years, resulting in a rainfall–runoff ratio that has been resilient to watershed changes. Reservoir sedimentation rates generally were higher before 1963, but have been much lower and very stable since that time. Our findings suggest that (1) rangeland water yields may be stable over long periods despite dramatic landscape changes while (2) these same landscape changes influence sediment yields that impact downstream reservoir storage. Relying on rangelands to meet water needs demands an understanding of how these dynamic landscapes function and a quantification of the physical processes at work.

scholarly journals Do Land Use Changes Balance out Sediment Yields under Climate Change Predictions on the Sub-Basin Scale? The Carpathian Basin as an Example

Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1499 ◽  
Author(s):  
Paulina Orlińska-Woźniak ◽  
Ewa Szalińska ◽  
Paweł Wilk
Keyword(s):  
Land Use ◽  
Sediment Yield ◽  
Assessment Tool ◽  
Land Use Changes ◽  
Carpathian Basin ◽  
Winter Period ◽  
Baseline Scenario ◽  
Sediment Yields ◽  
Basin Scale ◽  
Yield Responses

The issue of whether land use changes will balance out sediment yields induced by climate predictions was assessed for a Carpathian basin (Raba River, Poland). This discussion was based on the Macromodel DNS (Discharge–Nutrient–Sea)/SWAT (Soil and Water Assessment Tool) results for the RCP 4.5 and RCP 8.5 scenarios and LU predictions. To track sediment yield responses on the sub-basin level the studied area was divided into 36 units. The response of individual sub-basins to climate scenarios created a mosaic of negative and positive sediment yield changes in comparison to the baseline scenario. Then, overlapped forest and agricultural areas change indicated those sub-basins where sediment yields could be balanced out or not. The model revealed that sediment yields could be altered even by 49% in the selected upper sub-basins during the spring-summer months, while for the lower sub-basins the predicted changes will be less effective (3% on average). Moreover, the winter period, which needs to be re-defined due to an exceptional occurrence of frost and snow cover protecting soils against erosion, will significantly alter the soil particle transfer among the seasons. Finally, it has been shown that modeling of sediment transport, based on averaged meteorological values and LU changes, can lead to significant errors.

scholarly journals Storm-wise sediment yield prediction using hillslope erosion model in semi-arid abundant lands

2013 ◽  
Vol 8 (No. 1) ◽  
pp. 42-48 ◽  
Author(s):  
S. Fazli ◽  
H. Noor
Keyword(s):  
Soil Erosion ◽  
Sediment Yield ◽  
Land Surface ◽  
Soil Conservation ◽  
Soil Erodibility ◽  
Storm Events ◽  
Erosion Model ◽  
Sediment Yields ◽  
Slope Steepness ◽  
Erosion Models

Evaluation of soil erosion by existing models is needed as an important tool for managerial purposes in designation of proper water and soil conservation techniques. The present study aimed to assess the applicability of hillslope erosion model (HEM) as one of the newest erosion models for prediction of storm-wise sediment yield in Khosbijan rangeland with 20% slope steepness by using soil erosion standard plots. In order to run the model, runoff depth, land surface cover, soil texture, slope steepness and length were determined for 16 storm events. The results showed that the uncalibrated HEM did not simulate the observed sediment yields properly. Calibration of soil erodibility parameter and developing regression between observed and estimated data indicated that the model was capable of predicting sediment yield in plots by applying soil erodibility parameter of 0.15 with determination coefficient of 0.64 and estimate error of 40%. 

scholarly journals Spatio-temporal patterns of the effects of precipitation variability and land use/cover changes on long-term changes in sediment yield in the Loess Plateau, China

2017 ◽  
Author(s):  
Guangyao Gao ◽  
Bojie Fu ◽  
Murugesu Sivapalan
Keyword(s):  
Land Use ◽  
Surface Area ◽  
Loess Plateau ◽  
Sediment Yield ◽  
Land Surface ◽  
Sediment Load ◽  
Temporal Patterns ◽  
Precipitation Variability ◽  
Spatio Temporal ◽  
Annual Sediment

Abstract. Within China's Loess Plateau there have been concerted revegetation efforts and engineering measures over the last 50 years aimed at reducing soil erosion and land degradation. As a result, annual streamflow, sediment yield and sediment concentration have all decreased considerably. Human induced land use/cover change (LUCC) was the dominant factor, contributing over 70 % of the sediment load reduction, with reductions of annual precipitation contributing the remaining 30 %. In this study, we use data on 50-year time series (1961–2011), showing decreasing trends in the annual sediment loads of fifteen catchments, to generate spatio-temporal patterns in the effects of LUCC and precipitation variability on sediment yield. The space-time variability of sediment yield was expressed as a product of two factors representing: (i) effect of precipitation (spatially variable) and (ii) fraction of treated land surface area (temporally variable). Under minimal LUCC, annual sediment yield varied linearly with precipitation, with the precipitation-sediment load relationship showing coherent spatial patterns amongst the catchments. On the other hand, the effect of LUCC is expressed in terms of a sediment coefficient, i.e., ratio of annual sediment yield to annual precipitation, which is equivalent to the slope of the sediment yield-precipitation relationship. Sediment coefficients showed a steady decrease over the study period, following a linear decreasing function of the fraction of treated land surface area. In this way, the study has brought out the separate roles of precipitation variability and LUCC in controlling spatio-temporal patterns of sediment yield at catchment scale.

scholarly journals How does the suspended sediment yield change in the North Caucasus during the Anthropocene?

2021 ◽  
Author(s):  
Anatolii Tsyplenkov ◽  
Valentin Golosov ◽  
Pelagiya Belyakova
Keyword(s):  
Land Use ◽  
Suspended Sediment ◽  
Sediment Yield ◽  
Weather Conditions ◽  
Sediment Flux ◽  
Northern Caucasus ◽  
Land Use Impacts ◽  
North Caucasus ◽  
Sediment Yields ◽  
Suspended Sediment Yield

Quantifying and understanding catchment sediment yields is crucial both from a scientific and environmental management perspective. To deepen the understanding of land use impacts and climate change on sediment load, we explore mechanisms of the suspended sediment yield formation in the Northern Caucasus during the Anthropocene. We examine how sediment flux of various river basins with different land-use/landcover and glacier cover changes during the 1925-2018 period. Our analysis is based on observed mean annual suspended sediment discharges (SSD, kg·s−1) and annual fluxes (SSL, t·yr−1) from 33 Roshydromet gauging stations (Russia). SSL series have been analyzed to detect statistically significant changes during the 1925-2018 period. The occurrence of abrupt change points in SSD was investigated using cumulative sum (CUSUM) charts. We found that SSL has decreased by −1.81% per year on average at most gauges. However, the decline was not linear. Several transition years are expected in the region: increasing trends from the 1950s and decreasing trends from 1988-1994. Correlation analyses showed that variation in SSL trend values is mainly explained by gauging station altitude, differences in land use (i.e., the fraction of cropland), and catchment area. Nonetheless, more accurate quantifications of SSL trend values and more refined characterizations of the catchments regarding (historical) land use, soil types/lithology, weather conditions, and topography may reveal other tendencies.

scholarly journals An interactive atlas for marine biodiversity conservation in the Coral Triangle

2019 ◽  
Vol 11 (1) ◽  
pp. 163-174 ◽  
Author(s):  
Irawan Asaad ◽  
Carolyn J. Lundquist ◽  
Mark V. Erdmann ◽  
Mark J. Costello
Keyword(s):  
Biodiversity Conservation ◽  
Marine Protected Areas ◽  
Spatial Information ◽  
Marine Protected Area ◽  
Marine Ecosystem ◽  
Marine Biodiversity ◽  
Coral Triangle ◽  
Biodiversity Informatics ◽  
Conservation Values ◽  
Mpa Network

Abstract. An online atlas of the Coral Triangle region of the Indo-Pacific biogeographic realm was developed. This online atlas consists of the three interlinked parts: (1) Biodiversity Features; (2) Areas of Importance for Biodiversity Conservation; (3) recommended priorities for Marine Protected Area (MPA) Network Expansion (http://www.marine.auckland.ac.nz/CTMAPS). The first map, Biodiversity Features, provides comprehensive data on the region's marine protected areas and biodiversity features, threats, and environmental characteristics. The second provides spatial information on areas of high biodiversity conservation values, while the third map shows priority areas for expanding the current Coral Triangle MPA network. This atlas provides the most comprehensive biodiversity datasets that have been assembled for the region. The datasets were retrieved and generated systematically from various open-access sources. To engage a wider audience and to raise participation in biodiversity conservation, the maps were designed as an interactive and online atlas. This atlas presents representative information to promote a better understanding of the key marine and coastal biodiversity characteristics of the region and enables the application of marine biodiversity informatics to support marine ecosystem-based management in the Coral Triangle region.

scholarly journals Resilience Thinking Approach to Protect Marine Biodiversity in Small Islands: A Case of Gili Trawangan, Indonesia

2021 ◽  
Vol 933 (1) ◽  
pp. 012012
Author(s):  
LAA Bakti ◽  
Marjono ◽  
G Ciptadi ◽  
F Putra
Keyword(s):  
Coral Reefs ◽  
Local Governments ◽  
Marine Protected Area ◽  
Rapid Development ◽  
Marine Ecosystem ◽  
Tourism Industry ◽  
Customary Law ◽  
Marine Biodiversity ◽  
Small Islands ◽  
Resilience Thinking

Abstract This paper examines the resilience thinking approach to protect marine biodiversity in small islands with the case of Gili Trawangan, Indonesia, which is part of a marine protected area. The rapid development of the world’s tourism industry, the monetary crisis in 1997, national reforms in 1998, global warming, and the irresponsibility of local governments to enforce formal rules on marine resources, have had a tremendous impact on marine biodiversity on small islands like Gili Trawangan. This study uses a qualitative method, including stakeholder interviews, participant observation, stakeholder mapping, and local document collection. The collaborative effort that was built by local residents with foreign businesspersons, academics, non-governmental organizations, and the village government of Gili Indah, started in 2001 was intended to protect the marine ecosystem on Gili Trawangan from destructive fishing practices, to prevent the further degradation of marine biodiversity on the islands. Results of this study found several collaborative work initiatives in Gili Trawangan to meet the challenges, e.g., the institutionalization of customary law called “Awig-Awig” to regulate coral reef activities, enforcement of regulations on marine biodiversity such as coral reefs, strengthening institutional capacity, and restoring the degraded coral reefs ecosystem.

scholarly journals Contrasting watershed-scale trends in runoff and sediment yield complicate rangeland water resources planning

2016 ◽  
Author(s):  
M. D. Berg ◽  
F. Marcantonio ◽  
M. A. Allison ◽  
J. McAlister ◽  
B. P. Wilcox ◽  
...  
Keyword(s):  
Sediment Yield ◽  
Land Surface ◽  
Sediment Cores ◽  
Watershed Scale ◽  
Landscape Changes ◽  
Sediment Yields ◽  
Dynamic Landscape ◽  
Cesium 137 ◽  
Lead 210 ◽  
Runoff And Sediment Yield

Abstract. Rangelands cover a large portion of the earth’s land surface and are undergoing dramatic landscape changes. At the same time, these ecosystems face increasing expectations to meet growing water supply needs. To address major gaps in our understanding of rangeland hydrologic function, we investigated historical watershed-scale runoff and sediment yield in a dynamic landscape in central Texas, USA. We quantified the relationship between precipitation and runoff and analyzed reservoir sediment cores dated using Cesium-137 and Lead-210 radioisotopes. Local rainfall and streamflow showed no directional trend over a period of 85 years, resulting in a rainfall-runoff ratio that has been resilient to watershed changes. Reservoir sedimentation rates generally were higher before 1963, but have been much lower and very stable since that time. Our findings suggest that (1) rangeland water yields may be stable over long periods despite dramatic landscape changes while (2) these same landscape changes influence sediment yields that impact downstream reservoir storage. Relying on rangelands to meet water needs demands an understanding of how these dynamic landscapes function and a quantification of the physical processes at work.

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