Interactions of warming and altered nutrient load timing on the phenology of oxygen dynamics in Chesapeake Bay

The effects of nutrient loading on estuaries are well studied, given the multitude of negative water quality and ecosystem effects that have been attributed to excess nitrogen and phosphorus. A current gap in this knowledge involves the sensitivity of seasonal cycles of estuarine biogeochemical processes to direct (warming) and indirect influences (nutrient load timing) of climate change. We used a coupled hydrologic–biogeochemical model to investigate changes in the phenology of hypoxia and related biogeochemical processes in Chesapeake Bay under three different hydrologic regimes. Shifts to earlier nutrient load timing during idealized simulations reduced the overall annual hypoxic volume, resulting from discernable, but relatively small reductions in phytoplankton biomass and both sediment and water-column respiration. Simulated increases in water temperature caused an increase in spring/early summer hypoxic volume associated with elevated respiration rates, but an associated exhaustion of organic matter in the early summer caused a decrease in late summer/fall hypoxic volume due to lowered respiration. Warming effects on hypoxia were larger than nutrient timing effects in scenarios where warming was restricted to spring and when it was applied to all months of the year. These idealized simulations begin the process of understanding the potential impacts of future climatic changes in the seasonal timing of key biogeochemical processes associated with eutrophication.     

A High‐Resolution National‐Scale Hydrologic Forecast System from a Global Ensemble Land Surface Model

Warning systems with the ability to predict floods several days in advance have the potential to benefit tens of millions of people. Accordingly, large‐scale streamflow prediction systems such as the Advanced Hydrologic Prediction Service or the Global Flood Awareness System are limited to coarse resolutions. This article presents a method for routing global runoff ensemble forecasts and global historical runoff generated by the European Centre for Medium‐Range Weather Forecasts model using the Routing Application for Parallel computatIon of Discharge to produce high spatial resolution 15‐day stream forecasts, approximate recurrence intervals, and warning points at locations where streamflow is predicted to exceed the recurrence interval thresholds. The processing method involves distributing the computations using computer clusters to facilitate processing of large watersheds with high‐density stream networks. In addition, the Streamflow Prediction Tool web application was developed for visualizing analyzed results at both the regional level and at the reach level of high‐density stream networks. The application formed part of the base hydrologic forecasting service available to the National Flood Interoperability Experiment and can potentially transform the nation's forecast ability by incorporating ensemble predictions at the nearly 2.7 million reaches of the National Hydrography Plus Version 2 Dataset into the national forecasting system.     

Integrated water resource management at the industrial park level: A case of the Tianjin Economic Development Area

Water reuse and wastewater minimization are becoming increasingly important strategies for industrial parks. However, integrated industrial water management systems at an industrial park level have not yet been adequately investigated to determine synergies. This paper employs a case study of the Tianjin Economic Development Area (TEDA) to examine the importance of developing an integrated water resources management framework at the industrial park level. The paper presents a framework for effective and efficient management of water resources within an industrial park by taking a systems approach to conventional water management practices, designed to minimize industrial water use and maximize wastewater reuse among different tenants of an industrial park. The framework is composed of four elements: a management information system, policies and regulations, economic instruments and capacity building. The paper then considers how to implement such an integrated approach.     

Soil surface nitrogen losses from agriculture in India: A regional inventory within agroecological zones (2000–2001)

We present soil surface nitrogen (N) budgets for the agricultural sector of India, calculated as inputs minus outputs over 21 agroecological zones (AEZ), for 2000–2001. Nearly 35.4 Tg N was input from different sources, with output from harvested crops of about 21.2 Tg N. Soil surface N balance for agricultural lands showed a surplus of about 14.4 Tg. Livestock manure constituted 44% of total inputs, followed by 32.5% from inorganic fertilizer, 11.9% from atmospheric deposition and 11.6% from N fixation. Though the N balance was negative in some states, due to aggregation of states in agroecological regions, all regions showed surplus N loads, with a range of about 19–110 kg/ha. The lowest loads were found for AEZ 17 in the Eastern Himalaya, with 19 kg/ha surplus, and the highest surplus N load in AEZ 7 with 111 kg/ha in Deccan plateau and the Eastern Ghats. Temporal trends in fertilizer consumption from 1950–2000 for India suggested a massive increase of ～47-fold, whereas production of major crops, rice, wheat and maize, increased nearly ～4.0-, 10- and 6-fold, respectively. Fertilizer consumption patterns were highly concentrated in Tamilnadu (204.6 kg/ha), Haryana (132.0 kg/ha) and Punjab (148.6 kg/ha). The paper addresses the role of agricultural intensification and its implications for water quality in agroecological regions of India.     

Eco-Environmental benefit assessment of the western route in China's South-North Water Transfer Project

Assessing the benefits of China's South-North Water Transfer project (SNWT) requires successful integration of an analysis of economic and eco-environmental benefits (EEB). To attain such integration, it is necessary to assess the EEB in detail, after the economic benefits have also been thoroughly assessed. The shadow engineering and market value methods are the major EEB assessment methods used in this study. We have assessed the EEB of the forest and grassland ecosystems in the recipient regions of the Western Route Project (WRP) for 2020, 2030 and 2050. Finally, some proposals are also made for efficient and sustainable management of the WRP.     

The relationships of urbanization to surface water quality in four lakes of Hanyang,China

By converting rural land into urban land, urbanization impacts on surface water quality, because cities produce more pollutants than farmlands, especially heavy metals. Ways to reduce urbanization impacts on water quality are now being highlighted worldwide. Considering that land use can be a source or sink in pollution runoff, an understanding of the relationship between urbanization and surface water quality, as well as effects of specific land uses on water quality, is crucial. Corresponding management and controlling steps can then be put forward towards non-point source (NPS) pollution control and urban sustainable development. China has experienced rapid urbanization, especially since the 1980s. However, the environmental impacts of this process are not fully investigated. Hanyang, Hubei Province was selected as a typical city to study the impacts of urbanization on lake water quality. Pearson's correlation analysis was performed to elucidate the correlation between different land uses and water quality indicators at both whole lake watershed and small catchment scales. The results indicated that land uses play different roles, either source or sink, in pollution flow processes. Bottomland had a negative and residential land a positive correlation to most water quality indicators, especially heavy metals. These proved to be indicative and crucial land uses in NPS pollution control. Finally, a strategy for regulating urban land uses is proposed for improving surface water quality in cities similar to Hanyang, in southern China.     

Evaluating long-term hydrological impacts of regional urbanisation in Hanyang,China, using a GIS model and remote sensing

China has experienced a rapid urbanisation, especially since the 1980s; however, the environmental impacts of this process are not fully investigated. Hanyang (Hubei Province, south China) was selected as a typical case to investigate runoff and non-point source (NPS) pollution impacts of urbanisation. A water quality simulation model (L-THIA) was applied to determine the long-term implications of different degrees of regional urbanisation impacts on NPS pollutants. Land-use patterns in 1987, 1998 and 2003 were analysed to evaluate the temporal variation of urbanisation, and the precipitation dataset from 1975 to 2003 was used to estimate the mean annual runoff and NPS pollutants. The contributions of different land-use categories to average annual runoff and NPS pollutant production were assessed by the means of a regression model. Results show that urban/impervious lands increased by 30.4% between 1987 and 2003, with the most increase occurring in 1998–2003. Industrial and forestlands have the most and least impact, respectively, on mean annual runoff and NPS pollutants. A combination of L-THIA and the regression model was found to be useful as a decision support tool for regional and urban planning from the perspectives of water quality control.     

Water use efficiency of a mixed cropping system of corn with grasses

A new cropping system of corn mixed with grasses was tried to make full and efficient use of water and to ease environmental problems such as soil erosion by water and wind in grain and forage feed production practices. Field experiments were conducted to investigate the water use efficiency under this mixture cropping system. Six treatments with two replicates were arranged as: bare field, corn only, rye only, alfalfa only, rye–corn mixture and alfalfa–corn mixture. Lysimeters were used to measure different components of water consumption in the crop fields for water use efficiency estimation. From the yields and water consumption of crops under different treatments, combined water use efficiency of corn and grasses were estimated. The results showed that WUEs in the mixed cropping fields of corn–grasses were much higher than those in the fields where only corn or grass were grown. Averaged WUE was 3.71 kg/m³ from the corn and rye mixture fields, 30% higher than that from the plots where only corn or rye were grown. Averaged WUE was 4.55 kg/m³ from the alfalfa and corn mixture fields, 60% higher than that from the fields where only corn or alfalfa were grown. Under the same conditions of irrigation, yields from the rye and corn mixture plots increased by 33%, as compared with those from fields where only corn or rye were grown. The yields from alfalfa and corn mixture fields were 61% higher than those from fields where only corn or alfalfa were grown. The experimental results also indicated that corn and alfalfa mixture cropping is better than a corn–rye mixture system.     

The potential role of virtual water in solving water scarcity and food security problems in China

Water, as a source of food security, plays an essential role in ensuring sustainable food resources for a growing population. However, water scarcity has increasingly become a constraint to economic development, particularly food production. The water-food challenge is impending because of China's increasing population and water demand. The concept of virtual water is useful to analyze this problem. In this paper, the implications and policy relevance of virtual water are expounded. Based on imported food volumes, it is calculated that an annual average of 10.52 × 10⁹ m³ of virtual water embodied in imported wheat and maize in the period between 1990 and 2000 is equivalent to 23% of the annual average transfer water volume of the South-North Water Transfer (SNWT) project. Consequently, this 29.3 × 10⁶ ha of virtual land is equivalent to 19% of China's arable land in 2000. Using the grain import prediction and the agricultural production conditions of China, the virtual water equivalents of China in 2010 and 2020 are evaluated, and are about 88 × 10⁹ m³ in 2010 and 95 × 10⁹ m³ in 2020, respectively. Importing virtual water embedded in traded food can alleviate water stress and even achieve food security. Virtual water trade may compensate for water demands for not only the past but also the future. Meanwhile, water trade can store water in its virtual water form, enabling food storage to play a potential role in solving food problems, as well as promoting sustainability of water resources in China.     

Short reviews by the Editor

Soil desiccation is a major issue limiting development and sustainability of forest vegetation in the Loess Plateau of China. Better understanding of the mechanisms of soil desiccation in the Loess Plateau can help scientists and forest managers improve vegetation management practices. The arid soil layer is the ecological aftermath of intense soil desiccation due to disturbed plant succession and soil water reduction. The formation and types of arid soil layer in the Loess Plateau were investigated to determine major causes of soil desiccation and its impact on forest vegetation. The negative effects of soil desiccation on the ecological environment and forest vegetation mainly include drying microclimate, degrading soil quality, poor vegetation growth, difficult forest renewal from natural seed banks, making it even more difficult to reforest forest lands and grasslands following plant senescence. Low precipitation, high evaporation, soil and water losses, improper selection of vegetation types, and too high population density of trees are probably the major reasons for the arid soil layer. Proper selection of vegetation types, adjusting tree density and other management practices can reduce the negative effects of the arid soil layer on forest vegetation.