Comprehensive Analysis on the Hydrologic Alteration and Causes of River Runoff in Min River of the Yangtze River, China

The construction of water conservancy projects has changed the hydrological situation of rivers and has an essential impact on the river ecosystem. The influence modes of different factors on runoff alteration are discussed to improve the development and utilization of water resources and promote ecological benefits. The ecological, hydrological index change range method (IHA-RVA) and hydrological alteration degree method were comprehensively used to evaluate Min River's hydrological situation. Based on six budyko hypothesis formulas, the contribution rates of climate change and human activities to runoff change are quantitatively analyzed. The study showed that the runoff of Min River basin showed a significant decreasing trend from 1960 to 2019 and a sudden alteration around 1993; The overall alteration in runoff conditions was 45% moderate, and the overall alteration in precipitation was 37% moderate; Precipitation and potential evapotranspiration also showed a decreasing trend within the same period, but the overall trend was not significant; The contribution of climate alteration to runoff alteration is 30.2%, and the contribution of human activities to runoff alteration is 69.8%, human activities are the dominant factor affecting the alteration of runoff situation in Min River basin.

Improving Indicators of Hydrological Alteration in Regulated and Complex Water Resources Systems: A Case Study in the Duero River Basin

Assessing the health of hydrological systems is vital for the conservation of river ecosystems. The indicators of hydrologic alteration are among the most widely used parameters. They have been traditionally assessed at the scale of river reaches. However, the use of such indicators at the basin scale is relevant for water resource management since there is an urgent need to meet environmental objectives to mitigate the effects of present and future climatic conditions. This work proposes a methodology to estimate the indicators of hydrological alteration at the basin scale in regulated systems based on simulations with a water allocation model. The methodology is illustrated through a case study in the Iberian Peninsula (the Duero River basin), where different minimum flow scenarios were defined, assessing their effects on both the hydrological alteration and the demand guarantees. The results indicate that it is possible to improve the hydrological status of some subsystems of the basin without affecting the water demand supplies. Thus, the methodology presented in this work will help decision makers to optimize water management while improving the hydrological status of the river basins.

Hydrologic Alteration and Enhanced Microbial Reductive Dissolution of Fe(III) (hydr)oxides Under Flow Conditions in Fe(III)-Rich Rocks: Contribution to Cave-Forming Processes

Previous work demonstrated that microbial Fe(III)-reduction contributes to void formation, and potentially cave formation within Fe(III)-rich rocks, such as banded iron formation (BIF), iron ore and canga (a surficial duricrust), based on field observations and static batch cultures. Microbiological Fe(III) reduction is often limited when biogenic Fe(II) passivates further Fe(III) reduction, although subsurface groundwater flow and the export of biogenic Fe(II) could alleviate this passivation process, and thus accelerate cave formation. Given that static batch cultures are unlikely to reflect the dynamics of groundwater flow conditions in situ, we carried out comparative batch and column experiments to extend our understanding of the mass transport of iron and other solutes under flow conditions, and its effect on community structure dynamics and Fe(III)-reduction. A solution with chemistry approximating cave-associated porewater was amended with 5.0 mM lactate as a carbon source and added to columns packed with canga and inoculated with an assemblage of microorganisms associated with the interior of cave walls. Under anaerobic conditions, microbial Fe(III) reduction was enhanced in flow-through column incubations, compared to static batch incubations. During incubation, the microbial community profile in both batch culture and columns shifted from a Proteobacterial dominance to the Firmicutes, including Clostridiaceae, Peptococcaceae, and Veillonellaceae, the latter of which has not previously been shown to reduce Fe(III). The bacterial Fe(III) reduction altered the advective properties of canga-packed columns and enhanced permeability. Our results demonstrate that removing inhibitory Fe(II) via mimicking hydrologic flow of groundwater increases reduction rates and overall Fe-oxide dissolution, which in turn alters the hydrology of the Fe(III)-rich rocks. Our results also suggest that reductive weathering of Fe(III)-rich rocks such as canga, BIF, and iron ores may be more substantial than previously understood.

Influence of Hydrologic Alteration on Sediment, Dissolved Load and Nutrient Downstream Transfer Continuity in a River: Example Lower Brda River Cascade Dams (Poland)

Hydrologic alternation of river systems is an essential factor of human activity. Cascade-dammed waters are characterized by the disturbed outflow of material from the catchment. Changes in sediment, dissolved load and nutrient balance are among the base indicators of water resource monitoring. This research was based on the use of hydrological and water quality data (1984–2017) and the Indicators of Hydrologic Alteration (IHA) method to determine the influence of river regime changes on downstream transfer continuity of sediments and nutrients in the example of the Lower Brda river cascade dams (Poland). Two types of regimes were used: hydropeaking (1984–2000) and run–of–river (2001–2017). Using the IHA method and water quality data, a qualitative and quantitative relationship were demonstrated between changes of regime operation and sediment and nutrient balance. The use of sites above and below the cascade made it possible to determine sediment, dissolved load, and nutrient trapping and removing processes. Studies have shown that changes in operation regime influenced the supply chain and continuity of sediment and nutrient transport in cascade-dammed rivers. The conducted research showed that sustainable management of sediment and nutrient in the alternated catchment helps achieve good ecological status of the water.

Statistical analysis of maximum runoff of the Southern Buh River using the method of ‘Indicators of Hydrologic Alteration’

Knowledge of maximum river runoff trends is of great practical importance, especially for design and operation of hydraulic structures. This article presents the results of the research of the Southern Buh River's maximum runoff. The water of the river is widely used for hydropower engineering, industrial and municipal water supply, agriculture, irrigation, shipping, tourism etc. The research of the maximum runoff was based on the Indicators of Hydrologic Alteration (IHA) method which is widely used in the whole world. This method enables calculation of quantitative statistical characteristics of rivers', lakes', reservoirs' runoff and determination of the degree of their hydrological regime changes. The IHA is used for water bodies having natural or regulated runoff. However, the IHA method was not widely used in Ukraine before. The purpose of this publication is using the Indicators of Hydrologic Alterations method in order to study the characteristics of maximum runoff and their changes along the Southern Buh River. The research was carried out based on the data of observations at 5 gauge stations located along the Southern Buh River. The research uses the mean daily discharges that has been recorded since the beginning of observations up to 2018 and 2019 inclusive. The river's runoff at each of gauge stations was divided into five components: "Extremely low runoff", "Low runoff", "High runoff pulses", "Small floods", "Large floods". This made it possible to separate three classes of high (maximum) runoff, for which the IHA statistics were calculated, from the total runoff. It was discovered that the long-term high runoff changes differed in each of its three components, although they had general trends. The most significant changes were found for large floods, with no significant changes found for high runoff pulses. General trends of high runoff showed that over time the values of maximum discharges tend to decrease, with the increasing duration of high runoff periods. The values of the main statistical indicators of high runoff gradually increase from the river's source to its mouth, which fully corresponds to the physical and geographical conditions of its formation. Nevertheless, some features of high runoff were still found. Thus small floods and high runoff pulses have the largest duration in the upper reach of the river. On average, the Southern Buh River experiences large floods once in every 10 years, small floods - once in every 2 years, high runoff pulses - 4-8 times a year in its upper reach and 9-14 times a year in its middle reach.

Hydrological alteration: the missing dimension of water in wastewater treatment plants. The case of the Manzanares River in Madrid (Spain)

The effects of the discharge of wastewater treatment plants (WWTP) on the status of rivers have most commonly been focused on water quality. A very limited number of works have characterised the ability of treatment plants to modify flow patterns in the receiving rivers. This paper presents a methodology for the assessment of the hydrologic alteration caused by WWTP discharges, over a two-fold sequence. The first phase comprises the application of indicators derived from accessible data and informative of the capacity of treatment plants to produce significant flow alterations. The second phase, which may only be carried out when flow data in the receiving river is available, is based on the indicators of hydrologic alteration provided by the free software IAHRIS (6 indicators) and IHA (2 indicators), and on a new indicator proposed in this paper to obtain information of flow alteration at seasonal and monthly time scales. The procedure suggested in this work is applied to the Manzanares River (Central Spain), allowing the quantification of the flow alteration generated by the 12 WWTP which give service to Madrid city (3.8 million inhabitants): Large increases of annual water volumes (from 108 hm3 to 410 hm3); at a monthly scale (increase from 246% to 1516%); variability in flow decreases in wet years by up to 47% and increases in dry years by up to 380%; seasonal patterns is altered within an altered regime. Results of the analysis show: (i) the ability of the proposed methodology to characterise the modification of flow patterns due to WWTP discharges; (ii) the importance of assessing such changes when evaluating the environmental impact of treatment plants; (iii) the importance of designing preventive and mitigation measures which maintain the ecological integrity of river ecosystems in the receiving channels.

Linking Altered Flow Regimes to Biological Condition: an Example Using Benthic Macroinvertebrates in Small Streams of the Chesapeake Bay Watershed

Regionally scaled assessments of hydrologic alteration for small streams and its effects on freshwater taxa are often inhibited by a low number of stream gages. To overcome this limitation, we paired modeled estimates of hydrologic alteration to a benthic macroinvertebrate index of biotic integrity data for 4522 stream reaches across the Chesapeake Bay watershed. Using separate random-forest models, we predicted flow status (inflated, diminished, or indeterminant) for 12 published hydrologic metrics (HMs) that characterize the main components of flow regimes. We used these models to predict each HM status for each stream reach in the watershed, and linked predictions to macroinvertebrate condition samples collected from streams with drainage areas less than 200 km2. Flow alteration was calculated as the number of HMs with inflated or diminished status and ranged from 0 (no HM inflated or diminished) to 12 (all 12 HMs inflated or diminished). When focused solely on the stream condition and flow-alteration relationship, degraded macroinvertebrate condition was, depending on the number of HMs used, 3.8–4.7 times more likely in a flow-altered site; this likelihood was over twofold higher in the urban-focused dataset (8.7–10.8), and was never significant in the agriculture-focused dataset. Logistic regression analysis using the entire dataset showed for every unit increase in flow-alteration intensity, the odds of a degraded condition increased 3.7%. Our results provide an indication of whether altered streamflow is a possible driver of degraded biological conditions, information that could help managers prioritize management actions and lead to more effective restoration efforts.

An operational method for the ecohydrological classification of temporary rivers and streams

<p>Water courses that recurrently cease to flow represent a large part of drainage networks, and are expected to expand with global warming and increased exploitation of water resources. Common classifications of the regime of these temporary streams are based on the statistics of zero flow events. This is partly practical because these statistics can be obtained from flow records or model simulations and the results can be used for some environmental regulations or management purposes.</p><p>Nevertheless, it is well known that the main hydrological control on riverine aquatic life is the presence-absence of water rather than its flow regime. Disconnected pools that frequently remain in temporary streams after flow cessation provide valuable refuges for aquatic life, which can last up to all year round. An operational characterisation of the hydrological regime of temporary streams useful for ecological purposes must therefore take into account at least the three main aquatic phases that they undergo: flow, disconnected pools and dry stream bed. However, gauging stations and the derived hydrological models may only marginally inform about the possible occurrence of disconnected pools after the cessation of flow.</p><p>In order to facilitate the implementation of the European Water Framework Directive to the temporary streams, an operational approach has been developed to describe and classify the regime of temporary streams and to assess their degree of hydrologic alteration, relevant to aquatic life. This approach is encapsulated in the freely available TREHS software. The first step of this approach is the gathering of information on the frequency of the three aquatic phases using diverse sources of information, such as flow records and simulations, <em>in situ</em> observations, interpretation of aerial or terrestrial series of photographs, and interviews with local inhabitants or technicians familiar with the riverine systems. Up to six metrics describing these frequencies and their temporal patterns of occurrence are used to determine the natural and observed stream regime, and to assess the degree of hydrological alteration.</p><p>The combination of the complementary frequencies of the three main aquatic phases allows the description of the regime of every stream as a point in a ternary plot, where the three vertices of the triangle represent the perennial streams, the perennial pools and the terrestrial systems, respectively. This ternary plot assists the classification of the regime of any stream that takes into account the statistics of the main proxies of the occurrence of aquatic habitats. The TREHS software also provides a classification of the regimes in the ternary plot that groups the regimes of assumed ecological significance and uses terms that are conflict-free from the current classifications. Furthermore, TREHS users can easily define new regime classes in this plot according to the ecohydrological characteristics of their streams.</p>