Treated wastewater irrigation effect on soil, crop and environment： Wastewater recycling in the loess area of China

A study was carried out at the Loess Plateau in Dongzhi,China,to test the feasibility of using secondary treatment sewage effluent and to determine whether the water quality would then meet the recommended irrigation norm.Seven crops,including celery,wheat, maize,millet,apples,rapeseed and yellow beans,were tested in the study.Physical and chemical properties of the soil,crop yield and quality and leachate at different soil depths were measured.In most cases,the quality of the crops that made use of treated sewage was not distinctively different from those that did not use treated sewage.However,yields for the former were much higher than they were for the latter.Leachates at different soil depths were analyzed and the results did not show alarming levels of constituents.For a period of approximately 14 months,the treated sewage irrigation had no significant effect on the loess soil and no cases of illness resulting from contact with the treated sewage were reported.With treated sewage irrigation,a slight increase in the organic content of the soil was observed.     

Characterizing Drought in Irrigated Agricultural Systems: The Surface Water Delivery Index (SWDI)

Quantifying surface water shortages in arid and semiarid agricultural regions is challenging because limited water supplies are distributed over long distances based on complex water management systems constrained by legal, economic, and social frameworks that evolve with time. In such regions, the water supply is often derived in a climate dramatically different from where the water is diverted to meet agricultural demand. The existing drought indices which rely on local climate do not portray the complexities of the economic and legal constraints on water delivery. Nor do these indices quantify the shortages that occur in drought. Therefore, this research proposes a methodological approach to define surface water shortages in irrigated agricultural systems using a newly developed index termed the Surface Water Delivery Index (SWDI). The SWDI can be used to uniformly quantify surface water deficits/shortages at the end of the irrigation season. Results from the SWDI clearly illustrate how water shortages in droughts identified by the existing indices (e.g., SPI and PDSI) vary strongly both within and between basins. Some surface water entities are much more prone to water shortages than other entities based both on their source of water supply and water right portfolios.     

Irrigation Water Allocation Using an Inexact Two‐Stage Quadratic Programming with Fuzzy Input under Climate Change

Agricultural irrigation accounts for nearly 70% of the total water use around the world. Uncertainties and climate change together exacerbate the complexity of optimal allocation of water resources for irrigation. An interval‐fuzzy two‐stage stochastic quadratic programming model is developed for determining the plans for water allocation for irrigation with maximum benefits. The model is shown to be applicable when inputs are expressed as discrete, fuzzy or random. In order to reflect the effect of marginal utility on benefit and cost, the model can also deal with nonlinearities in the objective function. Results from applying the model to a case study in the middle reaches of the Heihe River basin, China, show schemes for water allocation for irrigation of different crops in every month of the crop growth period under various flow levels are effective for achieving high economic benefits. Different climate change scenarios are used to analyze the impact of changing water requirement and water availability on irrigation water allocation. The proposed model can aid the decision maker in formulating desired irrigation water management policies in the wake of uncertainties and changing environment.     

Acid sulfate soils and human health—A Millennium Ecosystem Assessment

Acid sulfate soils have been described as the “nastiest soils on earth” because of their strong acidity, increased mobility of potentially toxic elements and limited bioavailability of nutrients. They only cover a small area of the world's total problem soils, but often have significant adverse effects on agriculture, aquaculture and the environment on a local scale. Their location often coincides with high population density areas along the coasts of many developing countries. As a result, their negative impacts on ecosystems can have serious implications to those least equipped for coping with the low crop yields and reduced water quality that can result from acid sulfate soil disturbance. The Millennium Ecosystem Assessment called on by the United Nations in 2000 emphasised the importance of ecosystems for human health and well-being. These include the service they provide as sources of food and water, through the control of pollution and disease, as well as for the cultural services ecosystems provide. While the problems related to agriculture, aquaculture and the environment have been the focus of many acid sulfate soil management efforts, the connection to human health has largely been ignored. This paper presents the potential health issues of acid sulfate soils, in relation to the ecosystem services identified in the Millennium Ecosystem Assessment. It is recognised that significant implications on food security and livelihood can result, as well as on community cohesiveness and the spread of vector-borne disease. However, the connection between these outcomes and acid sulfate soils is often not obvious and it is therefore argued that the impact of such soils on human well-being needs to be recognised in order to raise awareness among the public and decision makers, to in turn facilitate proper management and avoid potential human ill-health.     

Field Evaluation of DRAINMOD 5.1 Under a Cold Climate: Simulation of Daily Midspan Water Table Depths and Drain Outflows1

Abstract: The hydrologic performance of DRAINMOD 5.1 was assessed for the southern Quebec region considering freezing/thawing conditions. A tile drained agricultural field in the Pike River watershed was instrumented to measure tile drainage volumes. The model was calibrated using water table depth and subsurface flow data over a two‐year period, while another two‐year dataset served to validate the model. DRAINMOD 5.1 accurately simulated the timing and magnitude of subsurface drainage events. The model also simulated the pattern of water table fluctuations with a good degree of accuracy. The R² between the observed and simulated daily WTD for calibration was >0.78, and that for validation was 0.93. The corresponding coefficients of efficiency (E) were >0.74 and 0.31. The R² and E values for calibration/validation of subsurface flow were 0.73/0.48 and 0.72/0.40, respectively. DRAINMOD simulated monthly subsurface flow quite accurately (E > 0.82 and R² > 0.84). The model precisely simulated daily/monthly drain flow over the entire year, including the winter months. Thus DRAINMOD 5.1 performed well in simulating the hydrology of a cold region.     

新疆城市污水处理方式及利用途径初探

奎屯市城市污水的处理现阶段采用一级处理后接生物稳定塘的处理工艺是较为适宜的,但要注意做好污水及处理水的排放监测,加强排水管理,今后要逐步完善为规范的二级处理工艺。对污水处理要制定切实可行的水污染防治规划,不拘泥于现有的排水方案和污水处理厂选址,在污水厂下游建设规范的污水库作为处理水资源化利用的必要措施。我区多数城市水污染防治路线与奎屯市有着相似性,对各城市污水处理方式及利用途径可采用此方法进行深入细致的研究论证,为未来城市污水的有效处理及无害化、资源化利用打下基础。     

Impact of untreated wastewater irrigation on soils and crops in Shiraz suburban area, SW Iran

In this study an assessment is made of the negative impacts of wastewater irrigation on soils and crops sampled along the Khoshk River channel in suburban area of Shiraz City, SW Iran. For this purpose, samples of soil profiles (0–60 cm in depth) and crops were collected from two wastewater irrigated sites and a tube well-irrigated (control) site. Total concentrations of the five heavy metals (Ni, Pb, Cd, Zn and Cr) and their phytoavailable contents were determined. The Pollution Load Indexes (PLIs) and Contamination Factors (CFs) for soils and Hazard quotients (ΣHQ) for some vegetables were also calculated. The results showed the use of untreated wastewater has caused the following changes as compared to control site: (1) a 20–30% increase in organic matter content of soil; (2) increase in pH by 2–3 units; (3) significant concentration increase in Ex-Ca especially in top layers of soil resulting in high CEC; (4) build up of heavy metals (notably Pb and Ni) in topsoil above Maximum Permissible Limits (MPLs) indicating a moderate contamination (PLI > 1, CF > 2.5); (5) contamination of some vegetables (spinach and lettuce) with Cd due to its high phytoavailability in topsoil causing a HQ > 1; (6) excessive accumulation of Ni and Pb in wheat due to continual addition of heavy metals through long-term wastewater application. The study concludes that strict protection measures, stringent guidelines and an integrated system for the treatment and recycling of wastewater are needed to minimize the negative impacts of wastewater irrigation in the study area.     

Hydrologic–Economic Model for Managing Irrigation Intensity in Irrigation Areas under Watertable and Soil Salinity Targets

This paper gives mathematical details and sample applications of SWAGMAN Farm (SWAGMAN, Salt Water and Groundwater Management), a farm-scale hydrologic economic model that integrates agronomic, climatic, irrigation, hydrogeological and economic aspects of irrigated agriculture. The model is capable of determining optimum mix of land use to keep watertable and soil salinity within acceptable limits while maximising the economic returns. Alternatively, the model can simulate water and salt balance and economics of a given cropping preference. Web-based and Geographic Information Systems versions of the model are available for integration with the environmental reporting systems of the irrigation areas.     

Preliminary studies on potential remediation of acid mine drainage‐impacted soils by amendment with drinking‐water treatment residuals

Mining operations result in a wide range of environmental impacts: acid mine drainage (AMD) and acid sulfate soils being among the most common. Due to their acidic pH and high soluble metal concentrations, both AMD and acid sulfate soils can severely damage the local ecosystems. Proper post‐mining management practices are necessary to control AMD‐related environmental issues. Current AMD‐impacted soil treatment technologies are rather expensive and typically not environmentally sustainable. We conducted a 60‐day bench‐scale study to evaluate the potential of a cost‐effective and environment‐friendly technology in treating AMD‐impacted soils. The metal binding and acid‐neutralizing capacity of an industrial by‐product, drinking water treatment residuals (WTRs) were used for AMD remediation. Two types of locally generated WTRs, an aluminum‐based WTR (Al‐WTR) and a lime‐based WTR (Ca‐WTR) were used. Highly acidic AMD‐impacted soil containing very high concentrations of metals and metalloids, such as iron, nickel, and arsenic, was collected from the Tab‐Simco coal mine in Carbondale, Illinois. Soil amendment using a 1:1 Al‐ and Ca‐WTR mix, applied at 5 and 10 percent rates significantly lowered the soluble and exchangeable fractions of metals in the AMD‐impacted soil, thus lowering potential metal toxicity. Soil pH increased from an extremely acidic 2.69 to a near‐neutral 6.86 standard units over the 60‐day study period. Results from this preliminary study suggest the possibility of a successful scale‐up of this innovative, cost‐effective, and environmentally sustainable technology for remediating AMD‐impacted acid sulfate soils.     

Low-impact development for impervious surface connectivity mitigation: assessment of directly connected impervious areas (DCIAs)

Urbanization increases directly connected impervious area (DCIA), the impervious area that is hydraulically connected to downstream drainage by closed pipelines. Although the benefits of low-impact development (LID) have been examined in other studies, its effect on alleviating DCIA levels has seldom been assessed. This study measured the DCIA of urban watersheds in Houston, TX, USA. Five land-use types were categorized and the contribution of LID facilities to reducing DCIA in each type was estimated by using Sutherland's equations. The results showed (1) DCIA in commercial areas was greater than that in residential areas, especially for big-box retailers; (2) the percentage of DCIA reduction by LID varied by land-use type; and (3) optimal combinations of LID application could maximize the effectiveness of DCIA reduction. The results contribute to prioritizing land-use type for implementing LID practices and providing local governments with a useful measure to estimate runoff volume.