Impact Of Dams Research Articles

Effects of South-to-North Water Diversion Project Cascade Dams on Riparian Vegetation Along the Middle and Lower Reaches of the Hanjiang River, China.

The influence of the construction of dams for water diversion on the ecological environment has attracted recent widespread attention. Over time, dams have emerged as one of the most important factors affecting the vegetation along the riparian zones of rivers. To elucidate the effects of cascade dams on riparian vegetation along the middle and lower reaches of the Hanjiang River, we examined riparian vegetation types upstream and downstream from dams. A total of 14 sample sites and 131 quadrats perpendicular to the river were investigated in June 2019, and 14 sample sites and 134 quadrats were investigated in October 2019. The riparian vegetation was divided into 15 (in June) and 11 (in October) vegetation types by two-way indicator species analysis (TWINSPAN). Significant differences were found between the vegetation types upstream and downstream of dams. Redundancy analysis (RDA) showed that soil moisture content, distance from the water, altitude and soil total nitrogen (TN) were the main environmental factors affecting plants distributions, and soil moisture content was the main factor affecting the zonal distribution of vegetation. By analyzing the impact of cascade dams on the hydrological regime, we found that the construction of cascade dams led to the differentiation of vegetation types upstream and downstream of the dam, and the riparian habitats were fragmented by these dams. This study provides both an important reference for the protection of riparian vegetation and riparian ecosystems and a basis for the management and restoration of river ecosystems after the construction of cascade dams.

Satellite-Based Methodology for Purposes of Rescue Archaeology of Cultural Heritage Threatened by Dam Construction

The destruction of cultural heritage caused by dams represents a major issue especially in an age of climate change and narrowly focused development policies. To counteract this phenomenon, archaeologists and cultural heritage experts have relied upon rescue archaeology practices generally limited to fieldwork methodologies, while remote sensing of satellite imagery remains under-considered. To bridge this gap, we build on a multidisciplinary collaboration exploring the potential of Synthetic Aperture Radar (SAR) and open access multispectral satellite imagery, for quantifying the archaeological evidence located within a prospective reservoir area before dam construction. Based on previous research by Marchetti (2020) claiming the necessity for ad hoc protocols to document and monitor the impact of dams on cultural heritage, we selected two complementary situations: the planned dam of Halabiyeh in Syria and the under construction Grand Ethiopian Renaissance Dam (GERD) in Ethiopia. These case studies were analyzed with state-of-the-art methodologies to develop a feasible workflow that may contribute to fostering the use of satellite imagery in operational contexts such as those represented by these particular cases, and be replicated by archaeologists in other areas. The workflow is designed to be integrated to ground-truthing methodologies into two dedicated protocols named Pre-Construction Archaeological Risk Assessment (PCARA) and Pre-Flooding Rescue Archaeological Program (PFRAP) which could eventually become a standard procedure for rescue archaeology in dams areas.

Climate change and hydrological regime in arid lands: Impacts of dams on the plant diversity, vegetation structure and soil in Saudi Arabia

As the direct effects of climate change on the hydrological regime, Saudi Arabia has constructed more than 522 dams of various capacities as part of economic and environmental development. The study aims to assess the impact of dams on plant diversity, vegetation structure and soil in Saudi Arabia. Thirty-five stands were selected from the dams of different sizes of Saudi Arabia. Vegetation samples were established before (upstream) and after (downstream) the dam, and at the undammed (unaffected by the dam) to compare species diversity in the dam sites and undammed sites and to document the potential effects of dams on vegetation structure. A total of 151 plant species belonging to 36 families have been recorded. The vegetation associations are essentially shrubby with widespread annuals. Six novel associations were identified with the application of TWINSPAN, DCA, and CCA programs. They were named after the characteristic species as follows: VG I: Acacia gerrardii-Caralluma retrospiciens; VGII: Acacia tortilis-Maerua oblongifolia; VGIII: Lycium shawii-Farsetia aegyptiaca; VG IV: Farsetia stylosa-Cornulaca monocantha; VG V: Suaeda aegyptiaca-Salsola imbricata-Prosopis farcta and VGVI: Xanthium strumarium-Ochradenus baccatus. These plant communities are evaluated and discussed according to their floristic structure, vegetation diversity and edaphic variables. The riparian or streamside zones upstream and downstream that are periodically flooded contain highly diverse plant communities that are structured by flooding, which creates disturbance and acts as a dispersal mechanism for plants than undammed sites.

Climate change and the hydropower sector: A global review

AbstractRenewable sources of electricity, such as solar and wind, need to be paired with sources of reliable baseload. Hydropower is a renewable, low‐emission source of electricity baseload available throughout much of the world as an alternative to electricity conventionally provided by thermal combustion of fossil fuels; however, the global hydropower sector as it stands relies upon surface water flows of substantial and predictable volume. This makes it vulnerable to climate change. The impact of climate change on the hydropower sector is difficult to predict, and not globally uniform. It might be positive, negative, or inconsequential depending upon the local timing and magnitude of changes, reservoir size, allocation priority, and the energy market. The secondary effects of climate change on glacier lake outbursts floods, landslides, and sediment load are poorly understood. In addition, when planning hydropower projects for the future, attention must be given to the greenhouse gas contribution of the impounded waters behind storage dams, and the impact of dams on water temperature. In the past decade, sovereign nations and international development agencies worldwide have evaluated the potential of hydropower as a cost‐effective, clean, sustainable option for baseload electricity supply. There is therefore a crucial need to assess the opportunities and risks hydropower poses across a wide range of potential future climate conditions. This review paper conducts a global survey of the literature on the effect of climate change on hydropower and identifies room for improvement in current approaches to evaluation of the net benefits of hydropower projects under climate change.This article is categorized under: Vulnerability and Adaptation to Climate Change > Learning from Cases and Analogies Assessing Impacts of Climate Change > Evaluating Future Impacts of Climate Change

Berbagai Dampak Hukuman (Punishment) dalam Pendidikan Terhadap Peserta Didik

All humans are obliged to be educated. The objective of the subject of education is to improve the quality of oneself in order to become a complete person. In achieving that goal, education has tools to support its smooth running. One of the educational tools punishment which is punishment, has a profound impact on learners. The punishment in education is the punishment given to the learner aimed at edifying the offending learner. After the sentencing, the impact of the learner, the impact of each learner varied, to which in the study, researchers tried to dig up information on the impact of the punishment on the learner by using literature and secondary data, that is, data from previously existing sources such as journal articles, books, and scripts. Then the data was qualitatively analyzed using the miles and hubermans' methods. Analysis has resulted in some effect on learners. The effects are positive and dam impact.

Quantifying the impacts of climate variation, damming, and flow regulation on river thermal dynamics: a case study of the W\u0142oc\u0142awek Reservoir in the Vistula River, Poland

BackgroundRiver damming inevitably reshapes water thermal conditions that are important to the general health of river ecosystems. Although a lot of studies have addressed the damming’s thermal impacts, most of them just assess the overall effects of climate variation and human activities on river thermal dynamics. Less attention has been given to quantifying the impact of climate variation, damming and flow regulation, respectively. In addition, for rivers that have already faced an erosion problem in downstream channels, an adjustment of the hydroelectric power plant operation manner is expected, which reinforces the need for understanding of flow regulation’s thermal impact. To fill this gap, an air2stream-based approach is proposed and applied at the Włocławek Reservoir in the Vistula River in Poland.ResultsIn the years of 1952–1983, downstream river water temperature rose by 0.31 ℃ after damming. Meanwhile, the construction of dam increased the average annual water temperature by 0.55 ℃, while climate change oppositely made it decreased by 0.26 ℃. In addition, for the seasonal impact of damming, autumn was the most affected season with the warming reached 1.14 ℃, and the least affected season was winter when water temperature experienced a warming of 0.1 ℃. The absolute values of seasonal average temperature changes due to flow regulation were less than 0.1 ℃ for all the seasons.ConclusionsThe impacts of climate variation, damming, and flow regulation on river water temperatures can be evaluated reasonably on the strength of the proposed methodology. Climate variation and damming led to general opposite impacts on the downstream water temperature at the Włocławek Reservoir before 1980s. It is noted that the climate variation impact showed an opposite trend compared to that after 1980s. Besides, flow regulation below dam hardly affected downstream river water temperature variation. This study extends the current knowledge about impacts of climate variation and hydromorphological conditions on river water temperature, with a study area where river water temperature is higher than air temperature throughout a year.

Green spaces between water shortage and greed for urban sprawl, supported by fierce speculation: Case study, the city of M'sila

Water and green spaces have an existential, sometimes conflicting, relationship with urban sprawl, especially in regions with arid climates. Both are important elements of the urban composition that provide psychological and sanitary comfort and are economically, socially, and ecologically necessary for the population. By green space, we mean fruit trees and the cultivation of cereals and vegetables, which represent the main economic resource for the majority of the population of the city of M'sila. Our research aims to highlight the impact of the drop-in water from the Ksob dam. The only source of irrigation for climatic and management reasons, on the degradation of green spaces and their transformation into bare land without economic value, then into nurseries for urban planning. The consequences of the directives of the urban planning master plan (PUD 1976) are certainly catastrophic; water, demography, urban planning, and the future of the agro-pastoral vocation and green spaces of the city of M'sila. The data available and the technique used allowed us to include the period from 2017 to 2021. The numerical data shows the upward curve of urban expansion from 3,401.67 hectares to 3,969.28 hectares, the reduction of green spaces from 7,732.68 hectares to 3,802.77 hectares in just five years. There is similar trend for water which is reduced from 30 million m3 in 1972 to 3 million m3 in 2021, ten times less in 40 years. These figures reflect the seriousness of situation.

Livestock Owners' Perception on the Impact of Ghibe-III Hydroelectric Dam on Bovine Trypanosomosis, Southern Ethiopia.

Background:Trypanosomosis is an endemic livestock disease in Ethiopia. The problem prevails mainly in the South, Southwest, and Northwest regions following main rivers and their tributaries.Methods:A cross-sectional questionnaire survey was conducted in Loma and Kindo Didaye districts near the Ghibe-III hydroelectric dam, to compare dam impact upstream and downstream, from January 2019 to June 2020. Two hundred standardized questionnaire surveys were administered. The questionnaire included biography, livestock population before and after dam construction, knowledge of major livestock diseases, clinical signs, transmission, seasonality, and wildlife population status was assessed. Data were analyzed using Mann–Whitney U Test.Results and discussion:A total of 189 questionnaires were returned out of 200 questionnaires administered. Among the respondents, the majorities were males and had an average age of 39.4 + 10.6. In all herd size levels, there was no significant (P > .05) difference before dam construction between the 2 districts; whereas, statistically significant (P < .05) large and medium herd sizes increased by 16%(95% CI: 0.5, 31.5) after dam construction in Loma district; whereas, the same herd size reduced by 20%(95% CI:0,43.7) after dam construction with statistically significant(P < .05) difference. Bovine trypanosomosis ranked first among major diseases. Knowledge of clinical signs, transmission, and seasonality of trypanosomosis was consistent with the literature. 87.8% of respondents in Loma associated reduction of trypanosomosis and tsetse population, but 77% of Kindo Didaye respondents perceived no change in prevalence after dam construction. More reduction in wildlife population was observed upstream than downstream, health services improved, and disease outbreaks and cattle deaths were reduced. Studies in African countries indicate the reduction in tsetse apparent density and absences of wildlife contributed to the reduction of trypanosomosis.CONCLUSION:An increased herd size, reduced trypanosomosis prevalence, and wildlife population observed upstream, indicate artificial Lake has an impact on tsetse apparent density. Therefore, follow-up of the disease prevalence and investigation of drug resistance is recommended to prove the situation in the study area.

Analysis of Impact of Dams on The Environment

Analysis of Impact of Dams on The Environment

Impact of River Dams on Littoral Cells Located Adjacent to the River Mouth

Terrestrial sediment is a major source of sediment to all coasts. Suspended sediment is carried away by the rivers and supplied to the coast to maintain sediment budget. The construction of dams across the rivers arrest sediment behind it and affect the sediment budget of littoral cells along the coast. Reduction in sediment supply induces ecological as well as geomorphological changes along the shoreline. Coastal erosion may accelerate due to reduced sediment influx. With the growing number of cross-river dams and water diversion projects, it has become a major concern before the scientific community to measure, understand and find solutions to multi-fold geo-environmental problems that are arising out of river damming. The present study aims to find out the impact of dams on the coast. It examines how the changes in the suspended sediment supply of an Indian river impact the coast in terms of loss of area due to erosion. Temporal analysis of geomorphological changes along the shoreline in relation to sediment influx holds immense importance to coastal management essential for the sustainable life and livelihood of coastal communities. Scientific investigation into the impact of river dams on the coastal environment is likely to provide a strong ground to reconsider the way present basin development projects function. Areal changes in littoral sediment cells adjacent to the river mouth have been quantified and correlated with changes in sediment influx. Changes along the shorelines have been detected through multispectral satellite images of Landsat belonging to different dates. Image processing and quantification of changes have been performed in QGIS 3.14 “Pi” platform. Virtual raster, raster calculator, field calculator and other required tools in QGIS were used during image processing.

Dynamic Flow Alteration Index for Complex River Networks With Cascading Reservoir Systems

AbstractLarge dams degrade the river’s health by heavily regulating the natural flows. Despite a long history of research on flow regulation due to dams, most studies focused only on the impact of a single dam and ignored the combined impact of flow regulation on a river network. We propose a new Dynamic Flow Alteration Index (DFAI) to quantify the local and cumulative degree of regulation by comparing the observed controlled flows with the naturalized flows based on a moving time horizon for the highly regulated Colorado River Basin. The proposed DFAI matches closely to dam’s localized regulation for headwater gages and starts to diverge as we move downstream due to increase in cumulative impact of the dams. DFAI considers the impact of dam operations on flow characteristics such as shifting of peak flow occurrence and dampening of peak flows. DFAI estimates the degree of regulation to be small for upstream dams and finds the maximum network regulation to be 2.52 years at Glen Canyon reservoir. DFAI also successfully captures the reduction in cumulative regulation when dam operations (e.g., Hoover Dam) bring the altered flow in synchronization with natural regime due to downstream flow requirements. The impact of San Juan River Basin Recovery Implementation Program is also captured by DFAI as the reduction in network regulation drops by 1.5 years for Navajo Dam. Our findings using DFAI suggest the need to develop naturalized flows for major river basins to quantify the flow alteration under continually changing climate and human influences.

ANALISI DAMPAK BENDUNGAN PANDANDURI TERHADAP USAHATANI PADI SAWAH DI KECAMATAN SAKRA BARAT KABUPATEN LOMBOK TIMUR

This study aims to determine the impact of the Pandan Duri dam on changes in the Crop Index (IP) and changes in the productivity level of rice paddy farming in West Sakra District, East Lombok Regency. The method in this research is descriptive, data collection is done by survey technique. Determination of the number of samples as many as 30 people is done by sampling quota and taking farmers in each village is done by proportional random sampling and determining the village as a sample is done by purposive sampling. The results showed that: 1) The total planting index (IP) of lowland rice before the Pandan Duri dam in West Sakra District was 1.39 and after 2.12. This means that the existence of the Pandan Duri dam can have an impact on the difference in the Crop Index (IP) of lowland rice farming in Sakra District and, 2) The average productivity of rice before the Pandan Duri dam in West Sakra District was 49,682 Kw/Ha while after the Pandan Duri dam was 57,267 Kw/Ha and there was a significant difference at the alpha 5% (0,05) level.or in the other word, that the existence of Pandan Duri development has real/significant impact on the productivity of lowland rice farming in West Sakra District, East Lombok Regency

Diversity in the observed functionality of dams and reservoirs

Abstract Knowledge and modeling of the observed functionality of dams and reservoirs are desirable for better water resources management. In this study, we examine the functionality of dams and reservoirs over much of the globe through a hydroclimate assessment over 990 Global Runoff Data Center stations that have at least one dam/reservoir over the corresponding drainage areas and available streamflow records of at least 25 years. To quantify the potential capacity of human disturbance/alteration, annual cumulative maximum storage (CMS) of the dams are computed and then annual potential changes in the residence time of water (PRT; CMS divided by annual mean monthly flow) are assessed. In addition, the Man–Kendall tests for annual maximum, mean, and minimum monthly streamflow, and drainage area-averaged precipitation are conducted. Results show that the size of CMS and the main purpose have an explanatory power of the designed hydrologic response (i.e., flattening of the seasonality) while 6% of dam-affected stations experienced the opposite hydrologic response (intensifying of the seasonality) due to the overwhelming impact of anthropogenic climate change. This study finds that the magnitude of PRT is a potential indicator to identify a considerable impact of dams and reservoirs for the regional hydrologic regime. The findings of this study suggest diversity in the observed functionality of dams and reservoirs, which is still a challenge in global hydrological modeling.

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.

Environmental impact of Aposelemis dam and tunnel water supply project in NE Crete, Greece

The current investigation concerns the impact observed at natural and human environment, due to the implementation of the Aposelemis water supply project, as additional aqueduct of Heraklion and Agios Nikolaos cities, as well as other important tourist areas, in NE Crete, Greece. Aposelemis project is differentiated from standard water supply dam projects, through a special component of an underground tunnel that diverts uphill surface water from Lasithi Plateau into the reservoir. The study concerns the first years of project’s operation, and focuses at four affected areas, namely the Lasithi Plateau upland area, dam’s region, river estuary and water supplied cities. The investigation was based on various site visits, while a significant aspect involves local stakeholders’ observation, opinion and perception on the environmental impact of the project in everyday life, through four detailed questionnaires posed to the affected areas’ population. The recorded consequences were characterized as positive or negative and evaluated according to their size and importance, estimated for the current period and also for the future. Among the main positive effects are urban areas’ drinking water supply and improved upland plateau’s flood water drainage, while among the negative consequences appear multiple water resources’ impacts and feelings of downstream lakeside residents. The investigation indicates the initial environmental impact and sets the basis for further future research towards sustainability.

The impact of dams on the river connectivity of the two largest river basins in China

AbstractDams are built on rivers for power generation, flood prevention and control, and water resources utilization. However, dams also reduce the connectivity of rivers, which hinders the exchange of material and organisms within rivers. The Yangtze River Basin and the Yellow River Basin are the two largest river basins in China. In this study, the connectivity of these two huge and highly impacted systems was investigated. The Dendritic Connectivity Index (DCI) was applied to evaluate the impact on river connectivity of dams with a reservoir capacity of larger than 0.1 km3. The results show that river connectivity decreased following an increase in dam construction. The connectivity of the Yangtze River Basin was close to 80 (0 is completely disconnected and 100 is connectivity under natural condition) in the 1980s, but declined significantly after the Gezhouba Dam was constructed on the mainstream of the Yangtze River. From 1980 to 2010, the connectivity of the Yellow River Basin was always lower than that of the Yangtze River Basin. The changes in the connectivity indices of potamodromous fish (DCIp) and diadromous fish (DCId) were determined for the period of 1980–2010. In the Yangtze River Basin, the DCIp decreased by 67.28% and the DCId decreased by 65.72%. In the Yellow River Basin, the DCIp decreased by 43.8% and the DCId decreased by 100%. In conclusion, the construction of dams, especially those on the main stream, has reduced the connectivity of the basin. The connectivity of the Yangtze River Basin and the Yellow River Basin has been severely affected.

Morphodynamic processes in rivers with cascade movable weirs – A case study of the middle Fen River

Cascade movable weirs have been increasingly widely used for river landscaping, water storage and ecological wellbeing. The weirs disturb the prior equilibrium in line with fluvial hydrology, sediment transport and geomorphology, and may lead to profound changes in the river, of which, however, the understanding has so far remained poor. Here, the first of its kind, a computational modelling study is presented on the morphodynamic processes under the impact of cascade hydraulic lifting dams, a type of movable weirs, as to the middle Fen River, China. A two-dimensional shallow water hydro-sediment-morphodynamic model is applied to resolve the fluvial processes, which is physically coupled and computationally efficient based on Finite Volume Method, unstructured mesh, local time stepping and parallel computing. Computational results show that the cascade dams alter the flow and sediment transport locally and on the reach scale in a distinct manner under different operation schemes, which in turn incur disparate morphological changes. Collapse of all the dams all year round would lead to net degradation in the study reach, with the floodplains aggrading and the main channel degrading. Operation of all the dams all year round may induce an overall aggradation both on the floodplains and in the main channel. If all the dams collapse in flood seasons and operate in dry seasons (CF), degradation occurs in the main channel whereas the floodplains experience aggradation, with a net degradation. When only the dams in the main channel operate all year round (OM), the floodplains degrade while the main channel aggrades, resulting in a net aggradation in the study reach. Either aggradation or degradation may prevail locally on floodplains, in main channel and individual subreaches. The present findings lead us to propose a complex operation scheme of annually alternating CF and OM to constrain significant morphological changes.

Fishway in hydropower dams: a scientometric analysis

Building dams for hydroelectric use causes several negative effects on the aquatic fauna with special attention to fish communities. In fact, among other impacts, dams act as a barrier for migratory fish, causing discontinuities in rivers and not allowing fish to move to the headwaters to breed and back to the lower portions of rivers, to grow. For more than 300years, fishways have been used to minimize the impact of dams. Here, we assess the worldwide knowledge about fishways, identifying the temporal and spatial pattern and the situation of Brazil in this global pattern. For this, we conducted scientometric research on the Web of Science repository with the following words: weir, fish, facilities, ladder, pass, dam, fish ladder, fish pass, fishway, hydropower, Petromyzon, and salmon between 1985 and 2019. Initially, we obtained 1282 articles. After a selection, 324 articles aimed to describe fishway efficiency and the relationship with the fish fauna remained. Most of the articles on dams, fishways, and fish are from North America and Europe. Among the articles in South America, most are from Brazil. Nonetheless, information on the topic is incipient in Brazil, since the country has one of the biggest hydropower in the world and 42 scientific articles about fishways published in the international scientific database. Ecology is the area of knowledge with most articles, with continuous growth in the last 10years. Studies in the field of ecology are strategical, as this field can integrate different areas of knowledge to test the efficiency of fishways in fish conservation and may be able to answer the question: "Are fishways an ecological trap?" Research focusing on this question is important to understand the efficiency of fishways to better evaluate solutions to minimize the negative effects of dams on fish and increase the effectiveness of fishways.

What Have We Lost? Modeling Dam Impacts on American Shad Populations Through Their Native Range

American shad (Alosa sapidissima) are native to the east coast of North America from the St. Johns River, Florida, to the St. Lawrence River region in Canada. Since the 1800s, dams have reduced access to spawning habitat. To assess the impact of dams, we estimated the historically accessed spawning habitat in coastal rivers (485,618 river segments with 21,113 current dams) based on (i) width, (ii) distance from seawater, and (iii) slope (to exclude natural barriers to migration) combined with local knowledge. Estimated habitat available prior to dam construction (2,752 km2) was 41% greater than current fully accessible habitat (1,639 km2). River-specific population models were developed using habitat estimates and latitudinally appropriate life history parameters (e.g., size at age, maturity, iteroparity). Estimated coast-wide annual production potential was 69.1 million spawners compared with a dammed scenario (41.8 million spawners). Even with optimistic fish passage performance assumed for all dams (even if passage is completely absent), the dam-imposed deficit was alleviated by fewer than 3 million spawners. We estimate that in rivers modeled without dams, 98,000 metric tons of marine sourced biomass and nutrients were annually delivered, 60% of which was retained through carcasses, gametes and metabolic waste. Damming is estimated to have reduced this by more than one third. Based on our results, dams represent a significant and acute constraint to the population and, with other human impacts, reduce the fishery potential and ecological services attributed to the species.

Impact of river dams on phosphorus migration: a case of the Pubugou Reservoir on the Dadu River in China

Reservoirs in agricultural catchments retain large proportions of inflowing phosphorus (P). However, the effects of reservoirs on the P cycle and related biogeochemical processes remain unclear. Therefore, this study investigated the degree to which a typical river-transition-reservoir in Southwest China retains both inflowing particulate phosphorus (PP) and dissolved total phosphorus (DTP) and various forms of P in sediments over different water seasons [normal-water season (NWS), low-water season (LWS), and high-water season (HWS)]. The proportions of inflowing PP and DTP retained were 37% and 27%, respectively. This result could be attributed to the absorption of DTP by the large load of intercepted sediment in the dam and the interception of PP itself. The rank of water seasons in terms of the proportion and load of inflowing TP retained was LWS (79%, 336 t P yr−1) > NWS (21%, 43 t P yr−1) > HWS (4%, 27 t P yr−1), which might be due to the high P concentration 0.78 mg L−1 and long hydraulic retention time (HRT) 780 d during the LWS. In the long-term, there was a high rate of retention of bioavailable phosphorus (BAP) in sediments (63%). This result could be attributed to the combined effect of fine sediment particles and organic matter (OM). In addition, HRT (R2 = 0.89, p < 0.05) affected the retention of P more significantly than P concentration (R2 = 0.56, p < 0.05). Dam interception during the LWS resulted in high BAP contents (280 mg kg−1) in sediments, high P concentrations (0.78 mg L−1), and weak hydrodynamics (HRT: 780 d) in overlying water. Therefore, further regulatory measures are urgently demanded during the LWS to prevent reservoir algal blooms.