Influence of saline intrusion during the dry season in Red riverand Thai Binh river systems, Vietnam

Debate exists about the effects of hydrological variation on food web dynamics and the relative importance of different sources of organic carbon fuelling food webs in floodplain rivers. Stable carbon isotope analyses and ecological stoichiometry were used to determine the basal sources in dry season macroinvertebrate food webs in two floodplain river systems of Australia’s wet–dry tropics that have contrasting flow regimes. Algae, associated with phytoplankton and biofilm, were the primary food source, potentially contributing >55% organic carbon to the biomass of a wide range of primary and secondary consumers. However, many consumers assimilated other sources in addition to algae, e.g. detritus from local C3 riparian vegetation. Food webs were characterised by substantial flexibility in the number and types of sources identified as important, which was indicative of generalist feeding strategies. These findings suggest ‘dynamic stability’ in the food webs, which imparts resilience against natural disturbances like flow regime seasonality and variation in hydrological connectivity. This adaptation may be characteristic of macroinvertebrate assemblages in highly seasonal river systems or in those with high levels of flow variability.

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Improving Carbonate Equilibria-Based Estimation of pCO2 in Anthropogenically Impacted River Systems

Frontiers in Earth Science ◽

10.3389/feart.2021.778215 ◽

2021 ◽

Vol 9 ◽

Author(s):

Omme K. Nayna ◽

Most Shirina Begum ◽

Lishan Ran ◽

Ji-Hyung Park

Keyword(s):

Water Pollution ◽

Organic Acids ◽

Monsoon Season ◽

Low Ph ◽

Dry Season ◽

River Systems ◽

Carbonate Alkalinity ◽

Han River ◽

Carbonate Equilibria ◽

Ph Range

Estimating riverine carbon dioxide (CO2) emissions has been constrained by lacking field measurements of the partial pressure of CO2 (pCO2) and inaccuracies in calculating pCO2 using carbonate equilibria-based models such as CO2SYS. To evaluate potential errors in applying the carbonate equilibria-based pCO2 calculation to river systems affected by monsoon rainfall and water pollution, we compared pCO2 values calculated using CO2SYS and those measured by headspace equilibration in five Asian rivers (Ganges, Mekong, Yangtze, Yellow, and Han rivers) undergoing various water pollution stages. Across the five rivers, calculated and measured pCO2 values exhibited larger discrepancies during the monsoon season, particularly in the low pH range, while in the Han River mismatches were also noticeable during the dry season. In the Han River, pH was negatively correlated with dissolved organic carbon (DOC) during the monsoon, indicating organic acids flushed from soils during rainfalls as a key factor for overestimated pCO2 at sites with low pH and alkalinity, whereas dry-season overestimation of pCO2 may be ascribed to non-carbonate alkalinity including organic acids and inorganic anions delivered by wastewater effluents or sporadic rainfalls. The four large rivers exhibited a positive correlation between pH and DOC in tributaries during the monsoon season, indicating that DOC flushed from soils may be diluted by monsoonal floods to such a degree as to exert little influence on pH and hence pCO2. Therefore, the monsoonal overestimation of pCO2 at sites with low pH and alkalinity warrants further investigation of other factors than non-carbonate alkalinity to explain the increased sensitivity of pCO2 to subtle changes in acidity and buffering. These results illustrate the importance of direct measurements of pCO2 in highly polluted rivers, especially during the monsoon season. For river systems lacking pCO2 measurements, we suggest that carbonate equilibria-based models be complemented with corrective measures: 1) presenting pCO2 values calculated from low pH values (pH < 6.5 for monsoon and pH < 6.3 for dry season) together with the pH range to warn potential overestimation; 2) using pre-established regressions between measured pCO2 and environmental variables to correct pCO2 values, particularly during wet periods when large changes in pH and acid buffering are expected.

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Nitrogen Removal by River Systems of the Feng River Basin in China

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1015.631 ◽

2014 ◽

Vol 1015 ◽

pp. 631-634

Author(s):

Jian Hui Zhi ◽

Ai Zhong Ding ◽

Shu Rong Zhang

Keyword(s):

Water System ◽

River System ◽

Dry Season ◽

River Network ◽

Nitrogen Loading ◽

Combined Processes ◽

River Systems ◽

N Removal ◽

N Input ◽

The Impact

As human activities continue to alter the global nitrogen cycle, the ability to predict the impact of increased nitrogen loading to river systems is becoming more and more important. Nitrogen retention is of particular interest because it is through its combined processes that local and downstream nitrogen concentrations are reduced. To determine the potential for N removed from Feng River network, we used stream chemistry and hydrogeo-morphology data from 17 stream and river sites to estimate NO3-–N removal in Feng River system of China. We used a N removal model to predict NO3-–N input and removal in December of 2011. NO3-–N input ranged from 0.06 to 20 kg km-1d-1in the Feng River system. Cumulative river network NO3-–N input was 446 ton year-1 in dry season in whole water system. NO3–N removal based on the model ranged from 0.04 to 4.2 kg km-1d-1 December of 2011 for Feng River. Cumulative river network NO3-–N removal predicted by the model was 58 ton year-1 in dry season. Proportional NO3–N removal (PNR) ranged from 0.2 to 0.6 in this time. PNR was negatively correlated with both stream orders.

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Monitoring saline intrusion in the Ayeyarwady Delta, Myanmar, using data from the Sentinel-2 satellite mission

Paddy and Water Environment ◽

10.1007/s10333-020-00837-0 ◽

2021 ◽

Author(s):

Toru Sakai ◽

Keisuke Omori ◽

Aung Naing Oo ◽

Yan Naung Zaw

Keyword(s):

River Water ◽

Water Resource Management ◽

Salt Water ◽

Absolute Error ◽

Dry Season ◽

Coefficient Of Determination ◽

Spatial And Temporal Variability ◽

Saline Intrusion ◽

Satellite Mission ◽

Sentinel 2

AbstractSummer rice cannot be grown near the coast of the Ayeyarwady Delta, Myanmar, because of the high salinity in river water during the dry season. This means that saline intrusion should be monitored to manage the irrigated rice-growing area. The aim of this study therefore is to develop a model to estimate the salinity of river water using satellite imagery. The imagery of Sentinel-2 was suitable for monitoring saline intrusion because of their high spatial (10-m) and temporal (10-day) resolutions. We found that the reflectance of the visible bands was correlated with electrical conductivity, which was influenced by the concentration and composition of dissolved salts. When the river water mixed with the salt water from the sea, suspended particles tended to flocculate and settle, as a result, less turbid water was more saline. The best-fitting model was obtained with the green band (coefficient of determination R2 of 0.776, root mean square error of 4.896 dSm−1, and mean absolute error of 3.340 dS m−1). The saline intrusion showed considerable spatial and temporal variability during the dry season. The salinity intrusion extended approximately 80 km inland at the end of the dry season in March in the Pathein River. The 1 ppt salt concentration line in March marked the boundary between cultivated and non-cultivated areas of paddy field, which indicates that cultivable areas were strongly affected by saline intrusion. The results show that more frequent and higher resolution monitoring than before of the Sentinel-2 can support effective water resource management.

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River dolphin distribution in regulated river systems: implications for dry-season flow regimes in the Gangetic basin

Aquatic Conservation Marine and Freshwater Ecosystems ◽

10.1002/aqc.1240 ◽

2012 ◽

Vol 22 (1) ◽

pp. 11-25 ◽

Cited By ~ 21

Author(s):

Sunil Choudhary ◽

Sushant Dey ◽

Subhashish Dey ◽

Viveksheel Sagar ◽

Tarun Nair ◽

...

Keyword(s):

Flow Regimes ◽

Dry Season ◽

Regulated River ◽

River Systems ◽

River Dolphin

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Evaluating salinity intrusion in estuaries using remote sensing data integrated in-situ observation

Science & Technology Development Journal - Science of The Earth & Environment ◽

10.32508/stdjsee.v2i2.493 ◽

2019 ◽

Vol 2 (2) ◽

pp. 50-56

Author(s):

Vu Nguyen Nguyen ◽

Trung Van Le ◽

Van Thi Tran

Keyword(s):

Remote Sensing ◽

Remote Sensing Data ◽

Principal Component ◽

Crop Productivity ◽

Dry Season ◽

In Situ Observation ◽

Landsat 8 ◽

Saline Intrusion ◽

Salinity Intrusion ◽

Actual Observation

Saline intrusion reduces crop productivity, causes land degradation, decreases water quality, and severely affects agricultural production, the environment as well as livelihoods. Under the evolution of climate change and human activities from the upstream of the Mekong, the downstream areas of Dinh An and Cung Hau estuaries in Tra Vinh province are also significantly affected by saline intrusion from the East Sea. This article presents the integrated solution of remote sensing and GIS in monitoring and mapping salinity intrusion. The data used are Landsat 8 satellite images combined with salinity water monitoring data collected from actual observation stations during the dry season. Analysis showed that there was a statistically significant correlation between the observed salinity value of the water and the pixel value of the first principal component image. Simulation of spatial distribution from the study indicates that saline intrusion is now entering the interior with a distance from the estuary to about 30 - 48 km depending on the time of the dry season. The results of this study will assist managers in planning food safety strategies at the risk of saline intrusion.

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