Effect of Check Dam on Sediment Load Under Vegetation Restoration in the Hekou-Longmen Region of the Yellow River

With years of vegetation restoration and check dam construction on the Loess Plateau, the sediment load of the middle reaches of the Yellow River have decreased sharply; however, the effects of check dam on this decrease of sediment load with such extensive vegetation restoration remains unclear. In order to further clarify the effects of check dam on sediment load reduction under vegetation restoration, we calculated vegetation coverage and check dam index based on multi-source remote sensing data, and calculated sediment reduction rate caused by human activities by Mann-Kendall statistical test and double cumulative curve, then established regression equations incorporating the check dam index and the sediment reduction rate using data from different geomorphic regions with different vegetation coverages. The results showed that sediment load in the Hekou-Longmen region and its 17 tributaries decreased significantly every year, and the change in sediment load could be divided into 3 typical periods: the base period (P1), the period mainly impacted by check dam construction (P2) and the period with comprehensive impact of check dam construction and vegetation restoration (P3). Compared with sediment load of the tributaries during P1, the sediment load decreased by 60.96% during P2 and by 91.76% during P3. Compared with the contribution of human activities to the reduction in sediment load in P2, the contribution of human activities in P3 increased significantly, while that of precipitation decreased slightly. The sediment reduction effect of check dams is greater in basins with low vegetation coverage than in basins with high vegetation coverage. There are differences in sediment reduction effect of vegetation restorations in different geomorphic regions, and the effect of vegetation restoration alone have certain upper limits. Such as, the upper limit of sediment reduction rate of vegetation restoration for rivers flowing through the sandstorm region is 47.86%. Hence, only combined the construction of check dam with vegetation restoration can it achieve more significant sediment reduction benefit and control soil erosion more effectively.

Analysis of Construction Implementation Time and Cost Scheduling by Adjusting Budget Changes Due to the Covid-19 Pandemic (Case Study on the Randugunting Dam Construction Project)

The Randugunting Dam, located in Blora Regency, is planned to have a capacity of 10.40 million m and is expected to irrigate an area of 630 Ha, providing a raw water supply of 0.15 m/second. The construction activity of the Randugunting Dam is one of the construction works that has been affected by the Covid-19 pandemic, namely cash flow is hampered. Therefore we need an analysis of cash flow management scenarios and determining strategies for handling the impact of the pandemic on implementation. The data used in this study is the result of interviews with the project implementation team for the Randugunting Dam construction, and data on the project cost budget. Cash flow management analysis is carried out by applying 3 scenarios, namely: scenario 1 (fixed time), scenario 2 (slowed down time), and scenario 3 (accelerated time). The analysis was carried out with the help of the Microsoft Project 2010. The determination of the handling strategy in this study used the DSS (Decision Support System) method, and the SWOT (Strength, Weakness, Opportunity, and Threat). The results of the study chose scenario 3, which is to speed up the time of 6 months. Acceleration is done by increasing the working time. The annual cost required is higher than scenario 1 (fixed time) and 2 (delayed time by 7 months), but the building is completed faster and can be used immediately. The strategy generated by SWOT analysis is Diversity Strategy and produces 8 (eight) strategies. Diversity Strategy is a strategy by maximizing internal strength factors (S), namely increasing the internal capabilities of project implementers and avoiding external threat factors (T), especially related to the Covid-19 pandemic.

Examining the Xayabouly dam: Impacts of hydropower dam construction on downstream communities

<p>Hydropower power dam development is a booming industry in Laos and it has the potential to tackle poverty in an environmentally sustainable way. However, currently there is a lack of research that thoroughly analyses the negative impacts of a hydropower dam’s construction phase. This research explores some of these negative impacts of hydropower dam construction on downstream villagers by using the Xayabouly hydropower dam on the Mekong River as a case study. Understanding the impacts of the construction phase is vital in forming policy and developing effective strategies to mitigate future negative impacts from dam construction. This thesis employs a qualitative approach and semi-structured interviews were conducted with downstream villagers about these negative impacts. This research is based on a pragmatist epistemology and employs the matrix conceptual framework to guide this thesis. The results from this study show that the Xayabouly hydropower dam’s construction phase has many negative impacts on downstream villagers’ daily lives. For example, the construction phase has caused irregular flooding, which has destroyed downstream villagers’ agricultural gardens and riverbank erosion has also occurred. Moreover, the results from this thesis show that the construction phase of this dam significantly reduced villagers’ income and nutrition consumption. The construction phase also created significant problems with regards to daily commuting and damaged fishing gear. These results offer important recommendations and implications, which have the potential to inform government policy in the future and to help develop strategies to mitigate the social and economic impacts from future hydropower dam construction in Laos.</p>

Examining the Xayabouly dam: Impacts of hydropower dam construction on downstream communities

<p>Hydropower power dam development is a booming industry in Laos and it has the potential to tackle poverty in an environmentally sustainable way. However, currently there is a lack of research that thoroughly analyses the negative impacts of a hydropower dam’s construction phase. This research explores some of these negative impacts of hydropower dam construction on downstream villagers by using the Xayabouly hydropower dam on the Mekong River as a case study. Understanding the impacts of the construction phase is vital in forming policy and developing effective strategies to mitigate future negative impacts from dam construction. This thesis employs a qualitative approach and semi-structured interviews were conducted with downstream villagers about these negative impacts. This research is based on a pragmatist epistemology and employs the matrix conceptual framework to guide this thesis. The results from this study show that the Xayabouly hydropower dam’s construction phase has many negative impacts on downstream villagers’ daily lives. For example, the construction phase has caused irregular flooding, which has destroyed downstream villagers’ agricultural gardens and riverbank erosion has also occurred. Moreover, the results from this thesis show that the construction phase of this dam significantly reduced villagers’ income and nutrition consumption. The construction phase also created significant problems with regards to daily commuting and damaged fishing gear. These results offer important recommendations and implications, which have the potential to inform government policy in the future and to help develop strategies to mitigate the social and economic impacts from future hydropower dam construction in Laos.</p>

Impacts of a large hydroelectric dam on the Madeira River (Brazil) on floodplain avifauna

ABSTRACT Hydroelectric dams represent an important threat to seasonally flooded environments in the Amazon basin. We aimed to evaluate how a dam in the Madeira River, one of the largest tributaries of the Amazonas River, affected floodplain avifauna. Bird occurrence was recorded through simultaneous passive acoustic monitoring in early successional vegetation and floodplain forest downstream from the dam and upstream in sites impacted by permanent flooding after dam reservoir filling. Species were identified through manual inspection and semi-automated classification of the recordings. To assess the similarity in vegetation between downstream and upstream sites, we used Landsat TM/ETM+ composite images from before (2009-2011) and after (2016-2018) reservoir filling. Downstream and upstream floodplain forest sites were similar before, but not after dam construction. Early successional vegetation sites were already different before dam construction. We recorded 195 bird species. While species richness did not differ between upstream and downstream sites, species composition differed significantly. Ten species were indicators of early successional vegetation upstream, and four downstream. Ten species were indicators of floodplain forest upstream, and 31 downstream. Seven of 24 floodplain specialist species were detected by the semi-automated classification only upstream. While we found some bird species characteristic of early successional vegetation in the upstream sites, we did not find most species characteristic of tall floodplain forest. Predominantly carnivorous, insectivorous, and nectarivorous species appear to have been replaced by generalist and widely distributed species.

Dam Break Analysis of Gembong Dam Using Zhong Xing HY21

Dams are a form of effort to conserve or protect water resources. The function of the Dam as a reservoir for water, irrigation, power generation, and flood control. However, in addition to its huge benefits, dam construction also can endanger the community’s safety, namely in the form of dam breaks. The main causes of dam break are overtopping and piping. So that analysis is needed related to dam break to minimize the impact. Based on the Zhong Xing HY21 software, the most severe impact of the break of the Gembong Dam was due to overtopping using the QInflow PMF design flood of 724.142 m3/s. It resulted in an inundation area of 54.682 km2 with a maximum inundation height of 5.129 m. As a result of the break of the Gembong Dam, 37 villages downstream of the Gembong Dam were flooded. There are 80.819 people affected by this risk. It is stated that all affected villages are at the 4th hazard classification level or very high hazard.

Impacts of hydropower on the habitat of jaguars and tigers

The rapid expansion of hydropower across tropical landscapes has caused extensive habitat loss and degradation, triggering biodiversity loss. Despite known risks to freshwater biodiversity, the flooding of terrestrial habitats caused by dam construction, and associated impacts on terrestrial biota, have been rarely considered. To help fill this knowledge gap, we quantified the habitat loss following inundation of hydropower reservoirs across the range of two iconic species, jaguars and tigers. To do so, we compiled existing and planned dams intersecting the distribution of these apex predators. We found 164 dams intersecting the jaguar range, in total flooding 25,397 km2. For tigers, we identified 421 dams, amounting to 13,750 km2. As hydropower infrastructure is projected to expand in the decades ahead, these values are expected to increase greatly, particularly within the distribution of jaguars where the number of dams will nearly quadruple (429 planned dams). Despite the relatively few dams (41) planned across the range of tigers, most will intersect priority conservation areas for this species. We recommend a more cautious pursuit of hydropower in topographically flat regions, to avoid extensive habitat flooding which has occurred in the Neotropics, and avoiding dam construction in priority conservation landscapes for tigers.

Impacts of dam construction on the macroinvertebrate community in the Poxin-Açú, in a tropical region

River regularization plays an important role in socio economic development. However, it also modifies the natural flow system of the river and its biotic and abiotic characteristics, causing significant impacts on rivers. To evaluate the impacts on the macroinvertebrate community caused by dam construction on the Poxim-Açú River, metrics of composition and community structure of the macroinvertebrates were analyzed, as well as ecological and biological traits of the region. Macroinvertebrates were collected at three sites located downstream the dam, before (2013) and after (2015) dam construction. The water quality was classified as “good” to “excellent” according to the biotics indices. The alterations of the flow regime of the river after the dam construction influenced the macroinvertebrate communities, modifying their diversity, equitability, richness, and the number of individuals. Keywords: bioindicators, dam impacts, environmental monitoring.

Multi-criteria approaches to identify the shoreline retreat downstream of dams: the North African case

Northern African beaches are among the most vulnerable areas under the extreme climate change hazard. Mainly sedimentary low-lying platform, the coasts are supplied by terrestrial yields, which are increasingly interrupted by dams. Unfortunately, the sediment fluxes are rarely measured and monitored, so that it is quite impossible today to assess the contribution of continental sediments to the coast and its variability. The aim of our study is to determine the sampling protocol of delta sedimentation plain and nearshore seabed for better understanding of the anthropogenic driver in contrast to climate change. We adopt a multi-criteria analysis based both on the geomorphologic feature and the historic evolution from the River to the littoral plain. The shoreline evolution reveals an alarming retreat trend reaching −20 m ± 0.15 m yr−1 after the human-induced change where ∼50 % of sediment discharge has been trapped upstream the dam, including quite all the coarse material, like sand. The shoreline retreat and the decreasing sediment rate of fluvial flow are all due to the dam construction.