Compounding soils to improve cropland quality:A study based on field experiments and model simulations in the loess hilly-gully region,China

Increasing the quantity and improving the quality of cropland can alleviate the human-land contradiction and promote the sustainable development of agriculture especially in mountainous areas.With the support of the central government’s policies,Yan’an,Northern Shaanxi,China implemented a major land consolidation engineering project in the loess hilly-gully region from 2013 to 2018,achieving 33,333.3 ha of new cropland.However,the poor quality of some newly-constructed cropland at the initial stage hindered its efficient utilization.In order to overcome this problem,red clay and Malan loess were compounded in different volume ratios to explore the method to improve the cropland quality.The Root Zone Water Quality Model was used to simulate the effects of different soil treatments on soil water,nitrogen and maize growth.Experimental data were collected from 2018 to 2019 to calibrate and validate the model.The root mean square error(RMSE)of soil water content,nitrate nitrogen concentration,above-ground biomass,leaf area index were in the range of 11.72-14.06 mm,4.06-11.73 mg kg^(-1),835.21-1151.28 kg ha^(-1)and 0.24-0.47,respectively,while the agreement index(d)between measured and simulated values ranged from 0.70 to 0.96.It was showed that,compared with land constructed with Malan loess only(T1),the soil structure and hydraulic characteristics of land with a volume ratio of red clay and Malan loess of 2:1(T3)was better.Simulation indicated that,compared with T1,the soil water content and available water content of T3 increased by 14.4%and 19.0%,respectively,while N leaching decreased by 16.9%.The aboveground biomass and maize yield of T3 were 7.9%and 6.7%higher than that of T1,respectively.Furthermore,the water productivity and nitrogen use efficiency of T3 increased by 21.0%and 16.6%compared with that of T1.These results indicated that compounding red clay and Malan loess in an appropriate ratio was an effective method to improve soil quality.This study provides a technical idea and specific technical parameters for the construction or improvement of cropland in loess hilly-gully region,which may also provide reference for similar projects in other places.

The Influence and Implications of Climate Change on Water Quality in a Large Water Reservoir in the Southwest, USA

Maintaining water quality in large reservoirs is crucial to ensure continued delivery of high-quality water to consumers for municipal and agricultural needs. Lake Mead, a large reservoir in the desert southwest, USA, is projected to be affected by both loss of volume and rising air temperatures through the end of the 21st century. In this study, reductions in lake volume, coupled with downscaled climate projections for rising air temperatures through the end of the 21st century, are incorporated into the 3D hydrodynamic and water quality model for Lake Mead. If current management practices continue in the future, simulations indicate water temperatures will increase in all scenarios and could increase by as much 2℃under the most pessimistic scenarios, but nutrient loads would not increase to concerning levels. Releases from the dam to downstream users are projected to be much warmer, and warmer water temperatures and significant dissolved oxygen in the water column are expected to cause challenges for ecosystem and recreation in the future. Surprisingly, during the Winter and Autumn, retention of heat in Lake Mead is more pronounced at higher surface elevations than the lower elevations as expected. The effects of these projections on the lake water quality and consequently, lake management decisions, are discussed.

Operational guidance for aeration and flow augmentation for the Chicago Area Waterway System—A case study

The Chicago Area Waterway System(CAWS)is a 133.9 km branching network of navigable waterways controlled by hydraulic structures,in which the majority of the flow is treated wastewater effluent and there are periods of substantial combined sewer overflows.The CAWS comprises a network of effluent dominated streams.More stringent dissolved oxygen(DO)standards and a reduced flow augmentation allowance have been recently applied to the CAWS.Therefore,a carefully calibrated and verified one-dimensional flow and water quality model was applied to the CAWS to determine emission-based real-time control guidelines for the operation of flow augmentation and aeration stations.The goal of these guidelines was to attain DO standards at least 95%of the time.The“optimal”guidelines were tested for representative normal,dry,and wet years.The finally proposed guidelines were found in the simulations to attain the 95%target for nearly all locations in the CAWS for the three test years.The developed operational guidelines have been applied since 2018 and have shown improved attainment of the DO standards throughout the CAWS while at the same time achieving similar energy use at the aeration stations on the Calumet River system,greatly lowered energy use on the Chicago River system,and greatly lowered discretionary diversion from Lake Michigan,meeting the recently enacted lower amount of allowed annual discretionary diversion.This case study indicates that emission-based real-time control developed from a well calibrated model holds potential to help many receiving water bodies achieve high attainment of water quality standards.

An Integrated Approach to Evaluate Benefits and Costs of Wastewater and Solid Waste Management to Improve the Living Environment: The Citarum River in West Java, Indonesia

Absence of wastewater and solid waste facilities impacts the quality of life of many people in developing countries. Implementation of these facilities will benefit public health, water quality, livelihoods and property value. Additional benefits may result from the potential recovery of valuable resources from wastewater and solid waste, such as compost, energy, phosphorus, plastics and paper. Improving water quality through implementation of wastewater and solid waste interventions requires, among others, an analysis of i) sources of pollution, ii) mitigating measures and resource recovery potentials and their effect on water quality and health, and iii) benefits and costs of interventions. We present an integrated approach to evaluate costs and benefits of domestic and industrial wastewater and solid waste interventions. To support a policy maker in formulating a cost and environmentally effective approach, we quantified the impact of these interventions on 1) water quality improvement, 2) resource recovery potential, and 3) monetized benefits versus costs. The integration of technical, hydrological, agronomical and socio-economic elements to derive these three tangible outputs in a joint approach is a novelty. The approach is demonstrated using the heavily polluted Indonesian Upper Citarum River in the Bandung region. Domestic interventions, applying simple (anaerobic filter) technologies, were economically most attractive with a benefit cost ratio (BCR) of 3.2, but could not reach target water quality standards. To approach the target water quality, both advanced domestic (nutrient removal systems) and industrial wastewater treatment interventions were required, leading to a BCR of 2. We showed that benefits from selling recovered resources represent here an additional driver for improving water quality and outweigh the additional costs for resource recovery facilities. While included benefits captured some of the major items, these may have been undervalued. Based on these findings, water quality interventions justify their costs and are socially and economically beneficial.

A review of hydrological/water-quality models

Water quality models are important in predicting the changes in surface water quality for environmental management.A range of water quality models are wildly used,but every model has its advantages and limitations for specific situations.The aim of this review is to provide a guide to researcher for selecting a suitable water quality model.Eight well known water quality models were selected for this review:SWAT,WASP,QUALs,MIKE 11,HSPF,CE-QUAL-W2,ELCOM-CAEDYM and EFDC.Each model is described according to its intended use,development,simulation elements,basic principles and applicability(e.g.,for rivers,lakes,and reservoirs and estuaries).Currently,the most important trends for future model development are:(1)combination models—individual models cannot completely solve the complex situations so combined models are needed to obtain the most appropriate results,(2)application of artificial intelligence and mechanistic models combined with nonmechanistic models will provide more accurate results because of the realistic parameters derived from nonmechanistic models,and(3)integration with remote sensing,geographical information and global position systems(3S)-3S can solve problems requiring large amounts of data.

The Hydrodynamic Behaviour of Euboean Gulf Coastal Areas and the Mixing of the Physico-Chemical Characteristics of Urban Sewage Discharged into Them under the Influence of Climate Change

The hydrodynamic circulation within the marine environment is a complex phenomenon, characterized by the interplay of strong tidal forces, atmospheric influences, and bathymetric features. The physical and hydrodynamic attributes of this flow play a pivotal role in promoting vertical mixing of seawater masses, thereby facilitating the integration of their physical and chemical parameters, including nutrients and oxygen. Additionally, they are instrumental in governing the dispersion and diffusion of pollutants originating from urban sewage, contributing to the overall water renewal process and environmental quality. This study investigates the potential impact of anticipated increases in average air temperatures on water column stratification in coastal regions susceptible to these dynamic influences. These areas receive treated urban sewage, and the study aims to assess how these temperature changes might influence the dispersion and mixing of pollutant loads present in these coastal waters.

Integration of USEPA WASP model in a GIS platform

The integration of water quality analysis simulation program (WASP) with a geographical information system (GIS) is presented.This integration was undertaken to enhance the data analysis and management ability of the widely used water quality model.Different types of data involved in WASP modeling were converted and integrated into GIS using a database method.The spatial data modeling and analysis capability of GIS were used in the operation of the model.The WASP water quality model was coupled with the environmental fluid dynamics code (EFDC) hydrodynamic model.A case study of the Lower Charles River Basin (Massachusetts,USA) water quality model system was conducted to demonstrate the integration process.The results showed that high efficiency of the data process and powerful function of data analysis could be achieved in the integrated model,which would significantly improve the application of WASP model in water quality management.

Ecological restoration for river ecosystems: comparing the Huangpu River in Shanghai and the Hudson River in New York

Starting in the 1960s,a great deal of effort and capital was invested in an endeavor to significantlyimprove the quality of surface water around the United States,particularly in metropolises like New YorkCity,New York.The Hudson River has been at the forefront of these efforts and has benefited immenselyfrom this campaign.In parts of the developing world,such as China,similar efforts are beginning to gatherthe same type of momentum.Within the past decade,the Huangpu River,which flows through Shanghaiinto the Yangtze Estuary of China,has been a target for ecological restoration and management.It is possibleto draw parallels between the cleanup efforts involved in improving the environmental conditions of theHuangpu and Hudson Rivers.Using the methodologies of series comparison(SCM),water quality index(WQI)modeling,consideration of ecological engineering,and policy strategy design,we comparativelystudied the topography,functions,environmental conditions,ecological engineering countermeasures,andmanagement policies of the two rivers to assist future forecasting of ecological restoration efforts in China.