PREDIKSI TINGKAT KEKERUHAN (TURBIDITAS) MENGGUNAKAN CITRA SATELIT SENTINEL-2A DI WADUK JATILUHUR, JAWA BARAT

Turbidity is one of the remote sensing indicators on the reservoir physical characteristics that can reduce its brightness level. Measuring reservoir physical characteristics traditionally are expensive and time consuming as well. Therefore, remote sensing is used as an alternative for turbidity measurement because it can provide data and products spatially, temporally as well as synoptically with low cost. This study aims to obtain an algorithm using a combination of in-situ turbidity data measurement and Sentinel-2A satellite imagery data. The resulting algorithm can be used to predict and map turbidity in Jatiluhur Reservoir. Based on the multiregression between B3 (green band) and B4 (red band) with in-situ turbidity data measurement, it is obtainted that the regression coefficients are a = 76.77, b = 63.22 and c = -34.31 respectively, with the equation of Y = 76, 77+63.22 X1-34.31X2 (Y=predicted turbidity, X1=lnB3, X2=lnB4). The correlation value between in situ and turbidity prediction is quite strong with a coefficient of determination (R2) of 0.60, and Root Mean Square Error (RMSE) of 1.95 NTU. Based on Mean Absolute Percentage Error (MAPE) analysis, the deviation is 31.1%. High levels of turbidity can reduce the main productivity of water and its organisms, especially in respiratory and visual problems. Sedimentation caused by high turbidity levels can make siltation which results in reservoir capacity loss.Keywords: Turbidity, remote sensing, Sentinel-2A satellite imagery data, Jatiluhur Reservoir, siltation

Sustainability of Engineered Rivers In Arid Lands

This interdisciplinary volume examines how nine arid or semi-arid river basins with thriving irrigated agriculture are doing now and how they may change between now and mid-century. The rivers studied are the Colorado, Euphrates-Tigris, Jucar, Limarí, Murray-Darling, Nile, Rio Grande, São Francisco, and Yellow. Engineered dams and distribution networks brought large benefits to farmers and cities, but now the water systems face multiple challenges, above all climate change, reservoir siltation, and decreased water flows. Unchecked, they will see reduced food production and endanger the economic livelihood of basin populations. The authors suggest how to respond to these challenges without loss of food production, drinking water, or environmental health. The analysis of the political, hydrological, and environmental conditions within each basin gives policymakers, engineers, and researchers interested in the water/sustainability nexus a better understanding of engineered rivers in arid lands.

To What Extent Can a Sediment Yield Model Be Trusted? A Case Study from the Passaúna Catchment, Brazil

Soil degradation and reservoir siltation are two of the major actual environmental, scientific, and engineering challenges. With the actual trend of world population increase, further pressure is expected on both water and soil systems around the world. Soil degradation and reservoir siltation are, however, strongly interlinked with the erosion processes that take place in the hydrological catchments, as both are consequences of these processes. Due to the spatial scale and duration of erosion events, the installation and operation of monitoring systems are rather cost- and time-consuming. Modeling is a feasible alternative for assessing the soil loss adequately. In this study, the possibility of adopting reservoir sediment stock as a validation measure for a monthly time-step sediment input model was investigated. For the assessment of sediment stock in the reservoir, the commercial free-fall penetrometer GraviProbe (GP) was used, while the calculation of sediment yield was calculated by combining a revised universal soil loss equation (RUSLE)-based model with a sediment delivery ratio model based on the connectivity approach. For the RUSLE factors, a combination of remote sensing, literature review, and conventional sampling was used. For calculation of the C Factor, satellite imagery from the Sentinel-2 platform was used. The C Factor was derived from an empirical approach by combining the normalized difference vegetation index (NDVI), the degree of soil sealing, and land-use/land-cover data. The key research objective of this study was to examine to what extent a reservoir can be used to validate a long-term erosion model, and to find out the limiting factors in this regard. Another focus was to assess the potential improvements in erosion modeling from the use of Sentinel-2 data. The use of such data showed good potential to improve the overall spatial and temporal performance of the model and also dictated further opportunities for using such types of model as reliable decision support systems for sustainable catchment management and reservoir protection measures.

Comparative overview of reservoir siltation assessment techniques depending on the type of sediment

<p>Over many decades it has become evident, that sediment accumulation threatens the fundamental operation of reservoirs by reducing the storage volume, hindering technical functions and deteriorating water quality over time. Most scientists, operators and authorities are aware of this, often “silent” but enduring process. However, not often mitigation measures are applied with foresight and in an appropriate manner according to this global problem. One fundamental reason for the often hesitant implementation of measures is the lack of precise and applicable assessment techniques. The type of reservoir, available historic data and especially the composition of the sediment may allow only for one available method to be applied successfully. In this study we present a workflow to select the best available method to detect the sediment thickness correctly. We compare topographic differencing, dual-frequency echo sounding, sub-bottom echo sounding, free-fall penetrometer measurements and sediment coring. Next to the general applicability, the precision (vertical resolution) and the time requirement for the measurement are relevant factors. A special point of discussion is the presence of free gas inside the sediment, often creating measurement errors, leading to underestimation of the sediment thickness.</p>

The Connection between a Suspended Sediments and Reservoir Siltation: Empirical Analysis in the Maziarnia Reservoir, Poland

This paper presents research on the influence of suspended sediments on selected aspects of a reservoir’s functioning. As the amount of sediment suspended in water (SS) there was found to correlate significantly with sedimentation rate (Us), it was possible to develop a function allowing the rate of accumulation of sediments to be predicted by reference to known amounts of suspended sediment. The latter factor was also shown to correlate significantly with the content of organic matter in suspension (OMSS), in sediment captured in a sediment trap (OMS), and of bottom sediment (OMSB). Analysis of amounts of suspended sediment can provide for estimates of total loads of organic pollutants deposited in the sediments of a reservoir. A further significant correlation with SS was noted for the concentration of total phosphorus in water (TPW), confirming the importance of internal production where the circulation of this biogenic substance in a reservoir ecosystem is concerned. Analysis of stable carbon isotopes in turn showed that entrapped sediments were depleted of—or enriched in—13C, in line with whether concentrations of total P in those sediments (TPS) were at their highest or lowest levels. This dependent relationship may thus be of key importance in assessing sources of phosphorus, as well as in forecasting concentrations present in reservoir sediments. The results obtained make it clear that sediments suspended in the water of a reservoir unify phenomena and processes ongoing there, between elements of the water-sediment system.

Mesoscale Mapping of Sediment Source Hotspots for Dam Sediment Management in Data-Sparse Semi-Arid Catchments

Land degradation and water availability in semi-arid regions are interdependent challenges for management that are influenced by climatic and anthropogenic changes. Erosion and high sediment loads in rivers cause reservoir siltation and decrease storage capacity, which pose risk on water security for citizens, agriculture, and industry. In regions where resources for management are limited, identifying spatial-temporal variability of sediment sources is crucial to decrease siltation. Despite widespread availability of rigorous methods, approaches simplifying spatial and temporal variability of erosion are often inappropriately applied to very data sparse semi-arid regions. In this work, we review existing approaches for mapping erosional hotspots, and provide an example of spatial-temporal mapping approach in two case study regions. The barriers limiting data availability and their effects on erosion mapping methods, their validation, and resulting prioritization of leverage management areas are discussed.

Mapping the future of offshore wind farming

Offshore wind farming is a growing presence in the renewable energy landscape but these ambitious projects rely on precise assessments of the hard to observe underwater landscape they will occupy before construction can even begin.<br/>Many governments around the world are moving toward renewable energy sources to meet their countries energy demands. The reasons behind this are many, ranging from reducing emissions to the safety of nuclear reactors and waste. For countries lying on or near fault lines, such as Taiwan, the latter becomes an even greater concern. When the earth shakes nuclear power plants, in particular, are highly sensitive and susceptible pieces of infrastructure. To avoid potential catastrophe and achieve greener energy sources the current government in Taiwan is aiming to phase out nuclear power in the coming years and they have chosen wind power as the technology to replace a large portion of the energy supply.<br/> In Taiwan the plan to phase of nuclear power and replace it with wind power has one extra challenge. The plan is not to build on land, like the majority of wind turbine projects, but rather to head out to sea. Offshore wind farms (OWF) are becoming a larger part of the wind power market and European countries have mostly been the early adopters. The waters off Taiwan, in the Taiwan Strait, are attractive for offshore wind farming development due to the favourable wind patterns that occur there. This has drawn major interest from European companies and others around the world to place bids on the growing number of wind farming projects. However, before any of these projects can take place an extensive effort to understand more about the environments below the surface must first be completed.<br/>Fortunately for those individuals who are curious as to the make-up and appearance of the ocean floor, such as engineers who plan to construct permanent structures in the depths, many techniques to map the seabed have been developed. Dr Gwo-Shyh Song, from The Institute of Oceanography at The National Taiwan University, in Taipei, is one local researcher who is very familiar with these methods. "I have been working on seafloor mapping around the Taiwan Island for last 20 years," points out Song. "This includes geophysical surveys, reservoir siltation surveys, cable and pipeline route surveys using a variety of techniques like multi-beam sounders and side-scan sonar as well as chirp sub-bottom profilers." When the offshore wind farming initiative needed experienced local researchers, he was one of a few people with the prerequisite expertise and technical skill required. "In 2012, when the OWF project was set into action and promoted by the Taiwanese Government, myself and my graduated students now employed within Global Aqua Survey Ltd started to become involved with many related investigatory projects," he explains.