Meander floodplain management and stabilization of riverbank in urban region

The normalization of the Meander River in the past caused environmental problems, changed the river’s ecology, and required heavy maintenance such as stabilizing riverbanks with revetments, sheet piles and other constructions. Pesanggrahan River, located at Southern Region of Jakarta, Indonesia which has a meander channel at the border between the middle reach and downstream reach. The river was normalized at the end of the year 2012 with several modifications such as resection, realignment and cutting-off meandering bends. Analysis the effect of normalization consisting of meander cut-off and riverbank stabilization presented in this paper in term of the behaviour of sediment transport along the channel that has been normalized. HEC-RAS program is used to track the Pesanggrahan river flow from upstream to downstream before and after normalization. The Ackers-White equation used to calculate the amount of sediment for each section based on the change of the river section due to sediment motion after normalizing of the channel river. From the results of the study, it is proposed that a river naturalization or low impact development (LID) approach, such as floodplain management especially at the meander bend with riparian ecosystems that maintain stabilization at the riverbank also maintain habitat heterogeneity, is an important factor for the long-term survival of several rare and endangered species.

Assessment of the Potential Natural Status of Riparian Zones in the Czech Republic

Riparian zones represent an important ecosystem providing a range of functions and services important to humans—e.g., biodiversity support, a reduction in erosion risk, or the transport of pollutants from the surrounding landscape to watercourses. At the same time, it is, unfortunately, an environment that has been often subjected to significant pressure during the agricultural cultivation of the landscape or the development of industrial and residential activities of human society. Thus, a large number of riparian ecosystems have disappeared or degraded. The assessment of the overall ecological status of riparian habitats constitutes an important source of information for the needs of watercourse management and landscape planning in the riparian landscape, the aim of which should be to maintain good status or to improve the current unsatisfactory state of these habitats. However, in order to reliably evaluate the current ecological status of the landscape, it is necessary to have information on the reference status, i.e., a potentially natural status that would prevail without human influence. For this purpose, a methodology that can determine the potential natural status of riparian zones in Central European conditions was developed. In this study, it was found that approximately a quarter (26 %) of all river basins in the Czech Republic reach very low environmental values of the potential natural status of riparian zones and, conversely, approximately 29 % of river basins are expected to develop significantly above average riparian zone quality if we neglect human impact.

Keanekaragaman Tumbuhan Fitoremediasi Di Ekosistem Riparian DAS Citarum

Riparian ecosystems have a protective function of watersheds from pollution. One important component in riparian ecosystem is the presence of phytoremediation plants, which can degrade contamination content. This research is intended to identify the presence of undergrowth that functions as phytoremediation in Bojongsoang District which is one of the areas around the heavily polluted Citarum watershed zone[1]. The method used in this research is vegetation analysis using the quadrant method with 1x1 m2 plot size. Determination of sampling points used purposive sampling method. The results of the study found that the undergrowth as a potential phytoremediation included rumput teki (Cyperus rotundus), Beluntas (Pluchea indica), Alang-alang (Imperata cylindrica), Jejarongan (Chloris barbata), rumput gajah (Cyperus rotundus), and bayam duri (Amaranthus spinosus). Rumput teki (Cyperus rotundus) is phyto-extractions in mercury-contaminated soils and accumulators of Sn, Zn, As, Cu, and Pb. Alang-alang (Imperata cylindrical) is a cyanide phytoremediator which is able to extract Zn from contaminated soil, and absorb Pb from contaminated soil. Beluntas is able to accumulate Cu, Fe, Al, Pb and Zn in their roots, leaves and stems, and the leaves that can absorb Cr. Rumput gajah (Cyperus rotundus) are a Cd accumulator. Bayam duri (Amaranthus spinosus) hyperaccumulator against mercury. Studies on the presence of phytoremediation plants can provide preliminary information on the condition of riparian ecosystems in the Citarum watershed.

Change point detection and Trend analysis of observed streamflow in the Upper Mekong Basin during the period 1960--2020

The Langcang-Mekong River Basin is the most important transboundary river basin in Asia. However, over the recent decades, dam construction has been increasingly recognized as having profound effects on hydrological processes, aquatic and riparian ecosystems. Understanding these impacts is critical for the foundation of sustainable runoff surface management. In this study, different methods based on both graphical and numerical techniques were applied to assess the effects of the dams on annual, seasonal, and monthly runoff and to detect hydroclimatic trends in the Upper Mekong Basin during the period 1960–2020. The results reveal two change points with respect to seasonal and annual flow regimes; that is 2003 for the flood season and annual flows, and 2013 for the dry season flow. The duration of the flood season and the volume of annual discharges have both significantly decreased since 2003 and the dry season discharge has significantly increased since 2013 (with both p-values < 0.05). The quantitative assessment suggests that, due to the effect of dams, the monthly discharges increased around 10–450 m3/s during the dry season (December to May), while the flood season’s monthly flows decreased significantly, approximately 1028–2150 m3/s from July to October at Chiang Saen station. The study of hydrological changes in the Mekong watershed is expected to be a significant contribution towards a better understanding of large watersheds in which the hydrological responses are influenced not only by climate change at large spatial and temporal scales but also by changes in the physical environment due to the construction of dams.

Herbicide-Resistant Invasive Plant Species Ludwigia decurrens Walter

Ludwigia decurrens Walter is a dicotyledonous plant belonging to the family Onagraceae. It is native to Central Eastern USA but has been spreading quickly and has naturalized in aquatic and riparian ecosystems (including rice paddy fields) in many countries; therefore, it is now considered an invasive noxious weed. L. decurrens is highly competitive with rice and causes a significant reduction in rice production. The objective of the present study was to evaluate the efficacy of the herbicide penoxsulam for the control of L. decurrens in rice fields. The seeds of L. decurrens were collected from four villages in Indonesia, and penoxsulam was applied to L. decurrens in seven dosages (0, 2.5, 5, 10, 20, 40, and 80 g a.i. ha−1) 3 weeks after seed sowing. The plant populations from Hegarmanah, Jatisari, and Joho showed complete mortality at the recommended dosage of penoxsulam (10 g a.i. ha−1). However, the plants from Demakan grew, flowered, and produced seeds 56 days after treatment with 40 g a.i. ha−1 of penoxsulam. The resistance index value of the population was 36.06. This is the first report of a penoxsulam-resistant weed from a dicotyledonous plant species and also the first report of a herbicide-resistant population of L. decurrens. The appearance of herbicide-resistant L. decurrens is a serious issue from both an environmental and an economic perspective, especially since protected forest and freshwater ecosystems are located at a short distance from the study area. Further research is needed to evaluate herbicide mixtures and/or the rotation of herbicide action sites. The identification of the penoxsulam-resistance mechanism in L. decurrens is also necessary to develop a herbicide resistance management strategy.

Conflicts in Implementing Environmental Flows for Small-Scale Hydropower Projects and Their Potential Solutions—A Case from Fujian Province, China

Releasing environmental flows is a valuable strategy for mitigating negative impacts of small-scale hydropower projects on river and riparian ecosystems. However, maintaining environmental flows has faced considerable resistance from different stakeholders, and previous studies have failed to appropriately investigate solutions. Here, online questionnaires and interviews were conducted among small-scale hydropower project owners, government administrators, and the public in Fujian Province, China. The results showed that the major hindrance to implementing environmental flows was the potential economic loss resulting from reductions in electricity production, stakeholders’ skepticism, technical difficulties, and a lack of the government supervision. Diversion-type projects pose the largest losses of electricity production after the release of environmental flows, and by adopting a 10% of mean annual flow as minimum target, most small-scale hydropower projects obtain low marginal profits without compensation. Here, we proposed an appropriate payment for ecosystem services by introducing an economic compensation program for different types of small-scale hydropower projects scaled by potential losses in electricity generation. Under such a scheme, economic losses from a reduction in electricity production are covered by the government, hydropower project owners, and electricity consumers. Our study offers recommendations for policymakers, officials, and researchers for conflict mitigation when implementing environmental flows.

Quantitative assessment of hydrological alteration over multiple periods caused by human activities at the Jingjiang Three Outlets, China

The Jingjang Three Outlets (JTO) play a major role in the water-sediment transport from the Yangtze River to Dongting Lake. The hydrological regimes at the JTO (Songzi, Taiping, and Ouchi) had been changed due to the Jingjiang Cutoffs (JC), the Gezhou Dam (GD), and the Three Gorges Dam (TGD). Based on hydrological data from 1955 to 2019, the variation trend in annual streamflow was detected using three techniques, and the hydrological alteration was assessed with the Range of Variability Approach. Conclusions are as follows: (1) the inflection points consistent with human activities and the time series were divided into periods of P1 (1955–1971), P2 (1972–1985), P3 (1986–2002), and P4 (2003–2019); (2) human activities made a greater contribution to streamflow change than climate change; (3) the hydrological alteration degree caused by the JC, GD, and TGD projects were 56%, 47%, and 52% at the Songzi outlet; 57%, 41%, and 57% at the Taiping outlet; and 57%, 41%, and 57% at the Ouchi outlet; and (4) the ability of division from the Yangtze River to Dongting Lake is weakening and the hydrological regimes at the JTO are deteriorating due to the JC, GD, and TGD, resulting in negative impacts on the biotic composition, structure, and function of riparian ecosystems. This study provides useful insight for ecosystem protection under hydrological alteration. HIGHLIGHT Quantitative assessment of hydrological alteration over multiple periods. Differentiated the influence of cutoffs projects and dam construction on hydrological alteration. Discussed the negative impacts of hydrological alteration on ecosystems and the countermeasures for future.