Making global river ecosystem health assessments objective, quantitative and comparable

Assessment of the anthropogenic interventions and related responses of Karala River, Jalpaiguri, India: a multiple indicator-based analysis

The sub-Himalayan foothill region is experiencing rapid land-use transformation over the last few decades resulting in the decay of several rivers such as Mahananda, Balason, Sahu, Rakti, Panchanai, Dharala, and Karala. A small rain-fed tributary of Teesta, Karala, has almost decayed in recent years but no notable assessment of its condition has been done to date. This study mainly aims to measure the intensity of human interventions and related responses of Karala through reach-wise, multiple indicator-based assessments. Initially, the reaches have been delineated by segmenting the river into 10 equidistant segments. Characterization of land-use and land-cover has been done for all such reaches. To determine the nature of hydro-geomorphology and water quality of the river 14 indicators are selected and categorized into 3 indices. According to the measured reach-wise mean (R_m), with the highest 4.70 (Reach 1) and lowest 2.21 (R9), it is clear that the need for restoration increases downstream since those areas portray massive deviation from least disturbed conditions (LDC). It is also revealed that the change in the bar area (ID7), vegetation condition (ID3), non-point sources of pollution (NPSP), and channel width (ID8) indicate also an alarming condition within the lower part of the river channel. It is evident that as the river approaches downstream, the natural state of landcover is lost due to intensive human intervention, mostly due to massive land-use transformation reflected in a 600% increase in built-up area in and around the Jalpaiguri region from 1990 to 2020. Hydrologically as well as ecologically sensitive rivers like Karala are the inseparable parts of the sub-Himalayan foothills. Degradation of such, due to, the human alteration would eventually disarrange the entire ecosystem. This easy-to-use, rapid, and coast effective methodology was found useful in distinguishing the extent of alterations by human intervention and the responses of such river systems.

Linking bait and feeding opportunities to fish foraging habitat for the assessment of environmental flows and river restoration

The survival of aquatic biota in different life history stages depends on food availability, water quantity and specific hydrological conditions, and is particularly susceptible in degraded rivers due to the development of hydropower or are sensitive to climate change. Habitats with limited food availability and restricted feeding opportunities can strongly affect the habitat carrying capacity and fish growth with consequences for spawning. Few environmental flow regime frameworks are available that closely link bait and feeding opportunities to fish foraging habitat. In addition, river restoration has been widely implemented to resolve the conflict between ecological demand and power generation benefits. Nevertheless, whether in-stream structures are still suitable for the joint operation of foraging and spawning habitats remains unclear. In this study, a framework to integrate the requirements of both spawning and foraging habitats into environmental flow regime assessments was proposed by coupling the bait supply, fish spawning and fish feeding opportunities. Here, we used the Batang Reservoir, located in the Tibetan Plateau, as an example to determine the environmental flow regimes. The environmental flow regimes during Periods I, II and III for the conservation of the life history stages of Schizothorax dolichonem were determined, which provided high-quality food and was beneficial for increasing the probability of restoration success. After the implementation of measures, the ecological base flow rate decreased from 171.80 m³/s, 206.00 m³/s and 257.70 m³/s to 138.00 m³/s, 206.00 m³/s and 206.00 m³/s in Periods I, II and III, respectively. We concluded that traditional river restoration with the use of in-stream structures is still suitable for the joint operation of spawning and foraging habitats, but the design selection and placement of in-stream structures should be preoptimized. The framework proposed will help managers evaluate habitat conservation to protect degraded rivers or help develop strategies to build resilience to climate change.

Assessment of Land Ecological Security and Analysis of Influencing Factors in Chaohu Lake Basin, China from 1998–2018

The land ecosystem provides essential natural resources for the survival and development of human beings. Therefore, land ecological security (LES) acts as a vital part of the sustainable development of human society and economy. This study included a dynamic analysis of land use change in Chaohu Lake Basin (CLB) in China from 1998 to 2018, evaluating the spatiotemporal patterns of LES at both the administrative district scale and grid scale (200 m × 200 m). Then, geographic detector was applied to analyze the influence of the assessment index on LES. The results show that in the 2008–2018 period, land use changed more significantly compared to the 1998–2008 period. The continuous extension of urban land led to a decrease in the areas of other land use types. In the CLB (administrative district scale), the LES levels varied throughout the study period. In Changfeng, Feixi, and the other three regions, the LES has been significantly improved. However, the LES in six other regions showed different degrees of decline, particularly in Hexian and Urban Hefei. Simultaneously, the LES showed a gradual improvement at a 200 m × 200 m grid scale level. The influence of anthropogenic factors on the LES was stronger than natural factors. Findings from this study provide reliable guidance for improving the ecosystem environment in ecologically fragile areas.

Application of Bipartite Networks to the Study of Water Quality

Water is a basic natural resource for life and the sustainable development of society. Methods to assess water quality in freshwater ecosystems based on environmental quality bioindicators have proven to be low cost, reliable, and can be adapted to ecosystems with well-defined structures. The objective of this paper is to propose an interdisciplinary approach for the assessment of water quality in freshwater ecosystems through bioindicators. From the presence/absence of bioindicator organisms and their sensitivity/tolerance to environmental stress, we constructed a bipartite network, G. In this direction, we propose a new method that combines two research approaches, Graph Theory and Random Matrix Theory (RMT). Through the topological properties of the graph G, we introduce a topological index, called J P ( G ) , to evaluate the water quality, and we study its properties and relationships with known indices, such as Biological Monitoring Working Party ( B M W P ) and Shannon diversity ( H ′ ). Furthermore, we perform a scaling analysis of random bipartite networks with already specialized parameters for our case study. We validate our proposal for its application in the reservoir of Guájaro, Colombia. The results obtained allow us to infer that the proposed techniques are useful for the study of water quality, since they detect significant changes in the ecosystem.

Study on Spatial and Temporal Distribution Characteristics of Coordinated Development Degree among Regional Water Resources, Social Economy, and Ecological Environment Systems

Water resources utilization, social economy development, and ecological environment protection are key factors in regional sustainable development. Scientific evaluation of regional coordinated development status and diagnosis of regional uncoordinated development constraints will improve the management level of decision-makers. At present, most developing countries have the problem of unbalanced regional development caused by the one-sided pursuit of a certain system. Taking 14 prefecture-level cities in Hunan Province as cases, this paper analyzed the spatial and temporal distribution characteristics of the carrying capacity level of the water resources system, the development level of the social economy system and the protection level of the ecological environment system in each evaluation unit based on entropy weight method and order parameter analysis. Based on the theory of coordinated development, a calculation model of a coordinated development degree was constructed, and the corresponding evaluation criteria were formulated. The spatial and temporal distribution characteristics of a coordinated development degree in each research unit were analyzed and evaluated. The results showed that the average coordinated development degree of Hunan Province from 2004 to 2016 evolved from "Light disorder recession" to "Nearly disorder recession", then to "Reluctance coordinated development". Restricted by different systems, the coordinated development degree in each research unit presented spatial and temporal differences. According to different development stages and the characteristics of different regions, corresponding development strategies can be formulated to provide the guidance for coordinated the development of regions.