The Influence of Channel Morphological Changes on Environmental Flow Requirements in Urban Rivers

Assessing river water quality for ecological risk in the context of a decaying river in India

The decay of rivers and river water pollution are common problems worldwide. However, many works have been performed on decaying rivers in India, and the status of the water quality is still unknown in Jalangi River. To this end, the present study intends to examine the water quality of the Jalangi River to assess ecological status in both the spatial and seasonal dimensions. To depict the spatiality of ecological risks, 34 water samples were collected from the source to the sink of the Jalangi River with an interval of 10 km while 119 water samples were collected from a secondary source during 2012-2022 to capture the seasonal dynamics. In this work, the seasonality and spatiality of change in the river's water quality have been explored. This study used the eutrophication index (EI), organic pollution index (OPI), and overall index of pollution (OIP) to assess the ecological risk. The results illustrated that the values of OPI range from 7.17 to 588, and the values of EI exceed the standard of 1, indicating the critical situation of the ecological status of Jalangi River. The value of OIP ranges between 2.67 and 3.91 revealing the slightly polluted condition of the river water. The study signified the ecological status of the river is in a critical situation due to elevated concentrations of biological oxygen demand, chemical oxygen demand, and low concentrations of dissolved oxygen. The present study found that stagnation of water flow in the river, primarily driven by the eastward tilting of the Bengal basin, triggered water pollution and ecological risk. Moreover, anthropogenic interventions in the form of riverbed agriculture and the discharge of untreated sewage from urban areas are playing a crucial role in deteriorating the water quality of the river. This decay needs substantial attention from the various stakeholders in a participatory manner.

Impact of Canal Encroachment on Flood and Economic Vulnerability in Northern Bangladesh

River and canal encroachments have become a common problem in Bangladesh. The prevalence of river and canal encroachments has a direct impact on population growth. However, the impacted population appears to be unaware of its negative consequences. To this end, we aimed to investigate the past and present canal scenarios with a focus on canal encroachment as the influencing factor in Ulipur upazila (highly vulnerable) of northern Bangladesh. To examine the impact of this encroachment, the Flood Vulnerability Index (FVI), Adaptive Capacity Index (ACI) and Economic Vulnerability Index (EVI) were used. Our results showed signs of narrowing of the canal structure of Ulipur upazila in 1982 and 1992, while satellite images from 2002 and 2012 showed the presence of encroachment in the middle and lower parts of the canal. The FVI value for Hatia union was 0.703, indicating that this area was highly vulnerable to flooding. According to the ACI, the Pandul union has a high capacity to cope with flood impact, while the Hatia union has less capacity to cope with flood impact. Conversely, Hatia’s union EVI value was 72.8, denoting a high economic vulnerability. Canal encroachments will have negative consequences for these impacted unions. It is critical to reduce the flooding and economic vulnerabilities associated with canal encroachments. It is found that canal excavation is very important for controlling flood water and reducing the damage caused by flooding.

Anthropogenic Activity Effects on Canals Morphology, Case Study: Nile Delta, Egypt

Waterways are usually contaminated with wastes from industrial, domestic or irrigation sectors. Organizations in charge have adopted solutions to eliminate this problem; however, the adopted solutions contribute indirectly to modifying canal morphology during maintenance. These are examples of anthropogenic activity, as well as randomly implemented dredging, which expand the canal cross-sections. Egypt is a country which depends on surface irrigation through a huge network of canals. The majority of canals in Egypt are subject to anthropogenic activity which affects their efficiency. This study aims to assess the impact of conjugated instances of anthropogenic activity and dredging on canal morphology and capacity. Five canals were selected in the current study in the Nile Delta, Egypt. These canals are highly affected by two associated factors: anthropogenic activity by users and dredging by the government. The study also aims to determine the effects of a newly adopted policy for saving surface water through restoration of the canals’ originally designed cross-sections. The results showed a clear change in canal morphology, which has increased the volume of water in the affected canals. In some cases, the volume of water has increased by 59%, which could have negative consequences for Egypt’s water resources. Sustainable management of water resources in Egypt requires saving each water droplet, and canal rehabilitation is expected to save about 6.56 million m3/year by the year 2022.

Evaluation of the Methodology to Assess the Influence of Hydraulic Characteristics on Habitat Quality

The article aims at assessing the impact of hydraulic characteristics on the habitat quality of mountain and piedmont watercourses. The solution results from the Riverine Habitat Simulation model, where the quality of the aquatic habitat is represented by the weighted usable area (WUA), which is determined using brown trout as the bioindicator. Flow velocity and water depth are basic abiotic characteristics that determine the ratio of suitability of the instream habitat represented by the weighted usable area. The influence of these parameters on the objective evaluation of the habitat quality is the essence of the paper. The measurements were carried out during the summer period at minimum discharges for 17 mountain and piedmont streams in Slovakia. Three methods for assessing the habitat quality were tested, and differences in the results were found to be significant. The evaluation shows the optimum design methods for calculating the weighted usable area.