Assessing ground water quality in the irrigated plain of Triffa (north-east Morocco)

Irrigated agriculture in (semi-)arid regions may exert serious pressures on groundwater resources and jeopardise further agricultural and socio-economical developments. For assessing these pressures, we present in this paper results from a groundwater quality survey performed in 2005 within the irrigated agricultural Triffa plain in north-east Morocco. The study focuses on the physico-chemical and bacteriological quality of the groundwater body within the plain and exploits the correlation and spatial dependency of the quality parameters. It is demonstrated that the water quality in this region is critical. Nitrate levels are situated between 2 and 153 mg/l, with 73% of the observations exceeding the critical level of 50 mg/l. Nitrite, ammonia, orthophosphate and dissolved organic matter content do not exceed existing norms. Bacteriological residues (faecal, total coliforms, faecal streptococcus and clostridium sulfido-reductants), however, are retrieved in nearly all water samples. Bacteriological contamination is merely correlated with nitrite and ammonia content rather than with nitrate content, indicating a possible contribution of local pollution sources to groundwater deterioration. The variability of the nitrate and bacteriological pollution is important and spatially correlated. The spatially dependency is modelled using spherical and Gaussian semi-variograms and is used to map the nitrate and bacteriological contamination using ordinary kriging techniques. The results shown are significantly different as compared to earlier studies on groundwater quality for the studied aquifer. The differences may be explained partially by modified but inappropriate fertilizer management practices in combination with intensive irrigation. Given the agricultural developments in this area, further deterioration of the groundwater quality is expected if no mitigation strategies are developed.     

The resource potential of in-situ shallow ground water use in irrigated agriculture: a review

Shallow ground water is a resource that is routinely overlooked when water management alternatives are being considered in irrigated agriculture. Even though it has the potential to provide significant quantities of water for crop use under the proper conditions and management. Crop water use from shallow groundwater is affected by soil water flux, crop rooting characteristics, crop salt tolerance, presence of a drainage system, and irrigation system type and management. This paper reviews these factors in detail and presents data quantifying crop use from shallow ground, and describes the existing state of the art with regard to crop management in the presence of shallow ground water. The existing data are used to determine whether in-situ crop water use from shallow ground water is suitable for a given situation. The suggested methodology uses ratios of ground water electrical conductivity to the Maas–Hoffman yield loss threshold values, the day to plant maturity relative to plant growth period, and the maximum rooting depth relative to the nearly saturated zone. The review demonstrates that for in-situ use to be feasible there has to be good quality ground water relative to crop salt tolerance available for an extended period of time. Shallow ground water availability is one area that can be managed to some extent. Crop selection will be the primary determinant in the other ratios.     

水资源水质水量优化配置分析

本研究旨在实现水资源水质水量的优化配置,通过对水资源水质水量优化配置的生态经济学理论进行分析,指出水资源水质水量优化配置的概念,在内涵分析基础上确定了水资源水质水量优化配置的具体阈值原理和模型体系框架.同时对青海水资源水质水量的优化配置进行分析,指出不同区域的水资源水质水量需要进行针对性的优化配置.     

Assessment of groundwater risk using intrinsic vulnerability and hazard mapping: Application to Souassi aquifer, Tunisian Sahel

Special attention has been paid to risk assessment in water resource management in arid and semi-arid regions like the Souassi aquifer, Tunisia. Risk assessment, using vulnerability and hazard mapping, is considered as a fundamental aspect of sustainable groundwater management. To determine the degree of risk affecting the study area, an attempt has been made to combine hydro-geologic parameters using the DRASTIC method and the hazard assessment by taking the product of the weighted hazard value (H_I), the ranking factor (Q_N) and the reduction factor (R_f).All parameters used in this risk assessment were prepared, classified, weighted and integrated in a GIS environment. Data treatment shows that large areas in the Souassi aquifer can be classified as high or very high risk areas corresponding to pollution sources located in high vulnerability zones. The areas with low and very low risk are situated in the south, which could, consequently, be interesting for future development and long term planning of protective measures. Sensitivity analyses indicated that the removal of groundwater depth, net recharge and aquifer media parameters from the DRASTIC index, causes large variation in vulnerability assessment. Moreover, hydraulic conductivity and topography were found to be more effective in assessing aquifer vulnerability. Therefore, they should have higher weights than those assumed by the DRASTIC standard method, and contrary to the impact of the vadose zone parameter. The validity of the DRASTIC and the risk methods, verified by comparing the distribution of nitrates in the groundwater and the different vulnerability classes, shows a high similarity.     

循环冷却水的水质稳定性处理

节约用水的最大潜力是节约工业冷却用水，而循环冷却水是节约水源的一条重要途径。但循环冷却水结垢、腐蚀现象严重，容易滋生菌藻，以致影响设备的传热效率，降低工效，缩短设备的使用寿命，因此，对循环冷却水进行水质稳定性处理是必不可少的，并在工业生产中得到应用，起到了节约用水、降低成本的作用，保证了长期安全可靠的生产，取得了良好的经济效益和社会效益。     

Controlled water table management as a strategy for reducing salt loads from subsurface drainage under perennial agriculture in semi-arid Australia

Recent community based actions to ensure the sustainability of irrigation and protection of associated ecosystems in the Murrumbidgee Irrigation Area (MIA) of Australia has seen the implementation of a regional Land and Water Management Plan. This aims to improve land and water management within the irrigation area and minimise downstream impacts associated with irrigation. One of the plan objectives is to decrease current salt loads generated from subsurface drainage in perennial horticulture within the area from 20 000 tonnes/year to 17 000 tonnes/year. In order to meet such objectives Controlled Water table Management (CWM) is being investigated as a possible ‘Best Management Practice’, to reduce drainage volumes and salt loads.During 2000–2002 a trial was conducted on a 15 ha subsurface drained vineyard. This compared a traditional unmanaged subsurface drainage system with a controlled drainage system utilizing weirs to maintain water tables and changes in irrigation scheduling to maximize the potential crop use of a shallow water table. Drainage volumes, salt loads and water table elevations throughout the field were monitored to investigate the effects of controlled drainage on drain flows and salt loads.Results from the experiment showed that controlled drainage significantly reduced drainage volumes and salt loads compared to unmanaged systems. However, there were marked increases in soil salinity which will need to be carefully monitored and managed.     

潮白河密云水库流域水质分析及环境影响因素研究

本文选取北京市密云水库及其上下游潮白河流域为研究区,基于不同河段、不同批次水样品的分析测定和生态环境调查,对主要水质指标进行对比分析.研究结果表明,密云水库上游及库区水质符合Ⅰ类、Ⅱ类地表水水质标准,满足饮用水源地要求,但个别观测点水质指标受环境影响存在较大差异.在密云水库下游,水质基本处于Ⅲ~Ⅴ类,水质指标更多受河道环境治理因素的影响.密云水库下游地区一些点位的指标,如溶解氧、氨氮和总磷较好,可见经过处理的中水作为景观用水用于改善生态环境具有现实意义.基于此,从污染治理、环境监管措施等方面为密云水库水源地保护提出建设性意见,提高水质,遏制生态环境恶化.     

中国省区虚拟水流动及对农业用水的影响

模拟省区间粮食虚拟水流动格局的基础上,从节水效应和对区域用水效率的改变2方面评价虚拟水流动对中国农业用水的影响.粮食虚拟水呈由北向南流动的总体格局,其中黑龙江与吉林贡献了虚拟水输出量的69.1%,广东、浙江、福建及上海占流入总量的56.2%;虚拟水在全国范围内节约了199.4亿m³的水资源;虚拟水流动提高了全部输入区的单位产品耗水(WFP)和用水量(WUP)和主要输入区的WFP,降低了除黑龙江、吉林之外所有输出区的WUP和WFP.各省区应根据自身状况和在虚拟水流动中的地位制定水资源高效利用与管理策略.其中,东北粮食主产区应从区域视角发展节水农业,提高农业的水资源利用效率.     

The impact of water and agriculture policy scenarios on irrigated farming systems in Italy: An analysis based on farm level multi-attribute linear programming models

The objective of this paper is to evaluate the impacts of agriculture and water policy scenarios on the sustainability of selected irrigated farming systems in Italy, in the context of the forthcoming implementation of the directive EC 60/2000. Directive EC 60/2000 (Water Framework Directive) is intended to represent the reference norm regulating water use throughout Europe. Five main scenarios were developed reflecting aspects of agricultural policy, markets and technologies: Agenda 2000, world market, global sustainability, provincial agriculture and local community. These were combined with two water price levels, representing stylised scenarios for water policy. The effects of the scenarios on irrigated systems were simulated using multi-attribute linear programming models representing the reactions of the farms to external variables defined by each scenario. The output of the models consists of economic, social and environmental indicators aimed at quantifying the impact of the scenarios on different aspects of sustainability relevant for irrigated farming systems. Five Italian irrigated farming systems were considered: cereal, rice, fruit, vegetables and citrus. The results show the diversity of irrigated systems and the different effects that water pricing policy may produce depending on the agricultural policy, market and technological scenarios. They also highlight a clear trade-off between socio-economic sustainability and environmental (water, nitrogen, pesticide) sustainability. Water pricing will have, in most cases, less impact than agricultural markets and policy scenarios, though it appears to be an effective instrument for water regulation in the least intensive irrigated systems considered. This emphasises the need for a differentiated application of the Water Framework Directive at the local level as well as a more careful balance of water conservation, agricultural policy and rural development objectives.     

The impact of controlled tidal exchange on drainage water quality in acid sulphate soil backswamps

Periodic opening of one-way tidal floodgates was undertaken on two coastal flood mitigation drains to promote exchange with estuarine water and improve drain water quality. The drains were located in areas with acid sulphate soils and their drainage water frequently had high acidity and low dissolved oxygen (DO). Tidal exchange via floodgate opening generally raised drain water pH levels through dilution and/or neutralisation of acidity. Increases in DO and moderation of extreme diurnal DO fluctuations were also observed. The magnitude and stability of the improved physico-chemical conditions was highly dependant on the volume and quality of tidal ingress water. Relatively rapid reversion (hours to days) in drain water pH and DO was observed once floodgates were closed again. The rate of reversion following floodgate closure was strongly related to outflow volumes, antecedent drain water quality conditions and groundwater levels. Floodgate opening caused changes in longitudinal drain water gradients and has potential to slow net drainage rates during non-flood periods. However, complex site specific interactions between drain water and adjacent groundwater can also occur. At one location, a 4-day floodgate opening event caused recharge of adjacent acid groundwater during the opening phase, raising the potentiometric groundwater level above local low tide minima. This was followed by tidally modulated draw down of acid groundwater and enhanced acid export in the period immediately following floodgate closure. There are also practical considerations, which limit the efficacy of floodgate opening as an acid management strategy. The low elevation (close to mean sea level) of some acid sulphate soil backswamps, combined with seasonal migration of the estuarine salt wedge, means there is considerable potential for saline overtopping of what is currently agricultural land. This constrains the magnitude and duration of controlled tidal exchange. Also, it is during wet periods that acid drainage outflow to the estuary is greatest. At such times the salinity and acid buffering capacity of estuarine water is often low, thus reducing the capacity of tidal exchange waters to neutralise acidity.     

灌溉水质和灌水方式对红壤斥水性及其理化性质的影响

以蒸馏水为对照,选取再生水和稀释2,4,6倍再生水等4种低质水,采用连续灌溉和再生水-蒸馏水交替灌溉等2种灌溉方式对红壤进行1年的处理,以此探明灌溉水质和灌水方式对酸性土壤斥水性、pH、盐分及有机质质量比的影响.结果表明:2种灌溉方式下红壤均产生亚临界斥水性,连续灌溉下红壤接触角比交替灌溉平均增加了23.1°;2种灌溉方式均使红壤酸性增强,盐分和有机质质量比增加,其中连续灌溉下的增长率大于交替灌溉下增长率;连续灌溉下红壤斥水性、pH、盐分和有机质质量比随灌溉水质的变化均可用二次函数来描述,决定系数均在0.9以上;交替灌溉下,红壤斥水性和盐分与灌溉水质的关系可用二次函数来表示,决定系数均在0.9以上,而土壤pH和有机质质量比与灌溉水质相关性不明显;2种灌溉方式下,红壤斥水性与pH呈负相关,与盐分质量比呈正相关,与土壤有机质质量比在连续灌溉下表现为正相关,而交替灌溉下则相反.采用再生水-蒸馏水交替灌溉方式能抑制土壤斥水性的产生.     

进入热泵机组的江水水质与过滤特性试验

为解决长江中上游的地表水中含沙量大,微生物以及悬浮物含量高,而不能直接作为江水源热泵机组的循环冷却用水的问题,对长江重庆段的水温和水质情况进行了分析,介绍了水流防堵除渣装置的原理,并通过试验测试了水流防堵除渣装置的性能.试验结果表明：过滤后的江水含沙量可降低到100 g/m3左右,平均去除率达68.5%,悬浮物及水藻含量也明显减少,浊度基本能够控制在50～100 NTU,平均去除率为73.1%,能够满足直接进入机组的水质要求.装置压力管道负载阻抗与安装管路特征阻抗相匹配,其水击压力幅值很小,能解决长江水进入热泵机组的清污、防堵、防水击的关键技术.整个分离系统结构简单,安装方便,运行可靠,运行费用低,能实现利用水流及重力完成浊水的自动过滤、自动清渣和自动排污,可在长江中上游的地表水源热泵中应用.     

武威市集中式饮用水源地水质空间分异规律

基于2013年16个地表地下水水源地监测断面水质实测资料,应用系统聚类R型主因子分析法和Ward法对武威市平原区集中式饮用水水源地水环境空间分异规律进行研究.结果表明:武威市平原区饮用水源地水质污染存在从北向南逐渐转移的趋势.2013年5月16个地表地下水监测断面水质污染从北边(西渠镇致祥供水站Bb5)向中部(校东桥Aa6、扎子沟Aa7)转移;2013年8月水质污染从中部(三雷镇新陶供水站Bb3、扎子沟Aa7)向南边(上坝水厂Ba5、南营水库Aa5)转移;其中主要污染物指标包括硝酸盐氮、高锰酸盐指数、氯化物、挥发酚、总大肠菌群、硫化物、硒、总硬度8项水质指标.研究结果可以对石羊河流域功能区的划分与该区域饮用水源地水环境综合治理提供依据.     

水肥耦合对温室番茄产量、水分利用效率和品质的影响

为指导日光温室番茄高产节水优质的灌溉施肥,以番茄为研究对象,设置3种施肥方式(总施肥量相同,施肥时间不同,其中F₁:不施底肥,番茄移栽后随水追施总肥量的30%,剩余70%平分6次追肥,F₂:底肥施1/2,剩余平分6次追肥,F₃:全施底肥不追肥)和3种土壤水势的灌水下限(W₁:-30 kPa,W₂:-50 kPa,W₃:-70 kPa),研究滴灌条件下水肥耦合对番茄耗水量、产量、水分利用效率和品质的影响.结果表明:施肥方式对番茄的耗水量差异不具有统计学意义,而灌水下限对耗水量有极显著性影响,且耗水量与灌水量呈极显著的正相关关系(P<0.01);与产量最大处理F₂W₁相比,F₂W₂处理产量降低6.91%,但节水14.83%,水分利用效率提高8.51%;TTS质量分数与平均单果重呈极显著负相关,而与除糖酸比外其他影响品质指标呈显著性正相关关系;综合考虑产量、WUE及TTS质量分数,利用TOPSIS综合评价方法,确定了温室滴灌条件下番茄节水调质的最优灌溉施肥模式为:移栽前施入底肥为总肥量的50%,移栽后灌水20 mm,进入开花坐果期以后,20 cm土层的土壤水势控制在-50 kPa以上,每次灌水定额为10 mm,剩余肥料每隔1次灌水追肥1次,将剩余50%的肥料分6次追肥.研究成果为制定日光温室番茄节水高产优质的灌溉模式提供了理论依据.     

Runoff, erosion, and water quality of agricultural watersheds in central Navarre (Spain)

Two experimental watersheds, La Tejería (1.69 km²) and Latxaga (2.07 km²), appointed by the Government of Navarre (Spain) for assessing the effect of agricultural activities on the environment, were monitored during 10 years (1996-2005). Both watersheds are roughly similar with regard to soils, climate (humid sub Mediterranean) and land use (almost completely cultivated with winter grain crops). The first results for both sites on runoff, exported sediment, nitrate and phosphate are presented.Most runoff, sediment, nitrate and phosphate yields were generated during winter, when variability was also the highest of the whole year.La Tejería had much higher sediment concentrations and sediment yield than Latxaga. Nitrate concentrations were also significantly higher at La Tejería, with values constantly over the critical threshold (>50 mg NO₃ l⁻¹). However, phosphate concentrations were similar in both watersheds and corresponded to water with a significant risk of eutrophication. Differences in watershed behaviour could be mainly due to differences in morphology, topography, and amount of stream channel vegetation between both sites.This is an unprecedented research for the region and the generated dataset is of paramount importance for research issues such as hydrology, erosion and water quality. The results highlight the complexity of Mediterranean agricultural landscapes and the need for further analyses to better ascertain the processes behind them.     

变化环境下农业需水量演变趋势及驱动力

根据宝鸡峡灌区11个气象站近30 a的气象及近20 a种植面积资料,分析了气候及作物种植结构的变化特征,计算了作物需水量和农业需水量,研究了灌区农业需水量的演变趋势,并利用主成分回归分析法揭示了影响农业需水量变化的驱动因素.结果表明:灌区气温呈显著上升趋势,相对湿度和风速呈显著下降趋势,蒸发量和日照时数略有增多,降水量有所减少.灌区农业种植结构变化较大,粮食作物与经济作物种植面积比例显著降低,由1991年的4.08减小为2010年的1.83;粮食作物与农作物总播种面积比例也呈下降趋势,由1991年的0.46减小为2010年的0.40.灌区小麦、玉米、油菜、棉花等4种主要作物需水量呈递增趋势,其中油菜需水量递增速率最快,约为3.558 mm/a;灌区农业需水量呈递减趋势,其递减速率为3.35×107m3/a.影响农业需水量变化的主要驱动因素为种植面积、降水量和蒸发量.降水量的减少和蒸发量的增多使得作物需水量明显增多,而农作物种植面积的减少,引起农业需水量的显著减少.     

湖库水质监测评价思考与建议

湖库水质评价是根据水体的用途,按照一定的评价参数、质量标准和评价方法,对水体进行定性和定量的评定.通过对数据的深加工处理,结合当地污染源排放状况、社会经济发展状况、区域内自然状况及其环境管理措施实施等信息的综合分析,客观合理地评价水环境质量状况,为环境管理及决策提供技术支撑.本文根据合肥市湖库水质环境监测评价的实际情况,提出几点关于湖库水质监测与评价的思考和建议.     

Cover crop effects on nitrogen load in tile drainage from Walnut Creek Iowa using root zone water quality (RZWQ) model

Studies quantifying winter annual cover crop effects on water quality are mostly limited to short-term studies at the plot scale. Long-term studies scaling-up water quality effects of cover crops to the watershed scale provide more integrated spatial responses from the landscape. The objective of this research was to quantify N loads from artificial subsurface drainage (tile drains) in a subbasin of the Walnut Creek, Iowa (Story county) watershed using the hybrid RZWQ-DSSAT model for a maize (Zea mays L.)-soybean [Glycine max (L.) Merr.] and maize-maize-soybean rotations in all phases with and without a winter wheat (Triticum aestivum L.) cover crop during a 25-year period from 1981 to 2005. Simulated cover crop dry matter (DM) and N uptake averaged 1854 and 36 kg ha⁻¹ in the spring in the maize-soybean phase of the 2-year rotation and 1895 and 36 kg ha⁻¹ in the soybean-maize phase during 1981-2005. In the 3-year rotation, cover crop DM and N uptake averaged 2047 and 44 kg ha⁻¹ in the maize-maize-soybean phase, 2039 and 43 kg ha⁻¹ in the soybean-maize-maize phase, and 1963 and 43 kg ha⁻¹ in the maize-soybean-maize phase during the same period. Annual N loads to tile drains averaged 29 kg ha⁻¹ in the maize-soybean phase and 25 kg ha⁻¹ in the soybean-maize phase compared to 21 and 20 kg ha⁻¹ in the same phases with a cover crop. In the 3-year rotation, annual N loads averaged 46, 43, and 45 kg ha⁻¹ in each phase of the rotation without a cover crop and 37, 35, and 35 kg ha⁻¹ with a cover crop. These results indicate using a winter annual cover crop can reduce annual N loads to tile drains 20-28% in the 2-year rotation and 19-22% in the 3-year rotation at the watershed subbasin scale over a 25-year period.     

Water reuse for irrigation in Jordan: Perceptions of water quality among farmers

The reuse of treated wastewater (reclaimed water) for irrigation is a valuable strategy to maximise available water resources, but the often marginal quality of the water can present agricultural challenges. Semi-structured interviews were held with Jordanian farmers to explore how they perceive the quality of reclaimed water. Of the 11 farmers interviewed who irrigate with reclaimed water directly near treatment plants, 10 described reclaimed water either positively or neutrally. In contrast, 27 of the 39 farmers who use reclaimed water indirectly, after it is blended with fresh water, viewed the resource negatively, although 23 of the indirect reuse farmers also recognised the nutrient benefits. Farmer perception of reclaimed water may be a function of its quality, but consideration should also be given to farmers’ capacity to manage the agricultural challenges associated with reclaimed water (salinity, irrigation system damage, marketing of produce), their actual and perceived capacity to control where and when reclaimed water is used, and their capacity to influence the quality of the water delivered to the farm.     

Sediment production and water quality of watersheds with contrasting land use in Navarre (Spain)

An experimental watershed (Oskotz principal- Op -ca.1700 ha) covered with forest and pasture (cattle-breeding) with an equally experimental sub-watershed (Oskotz woodland - Ow - ca. 500 ha) almost entirely under forest was continuously monitored during 8 years (2001-2008). These watersheds were established by the Government of Navarre (Spain) in order to assess the impact of agricultural activities on different region of Navarre. The first results regarding exported sediment, runoff, nitrate and phosphate are presented herein. These results are compared with those from two grain-sown watersheds previously reported by the authors, elsewhere.The same as in the grain-sown watersheds, most runoff, sediment, nitrate and phosphate yields in Oskotz were generated during winter, though most erosive rainfalls occurred during summer. In Ow, average sediment, nitrate and phosphate yields were approximately: 700, 22, 0.35 kg ha year⁻¹, respectively; for Op these figures were 550, 54 and 0.76 kg ha year⁻¹, respectively.However, total sediment and solute yields were different depending on the prevailing land use: cereal crops > forest > pasture. Sediment yields in the forest were strongly affected by the logging moment, when exported sediment rocketed.Nitrate concentration and yields were lower (and under the critical threshold) in the forested/pastured watersheds than those recorded in the two intensively cultivated watersheds. However, phosphate yields were dramatically higher (and over the critical threshold) in the former watersheds due to the prevailing soil conditions and to the fertilization of pasture, mainly with slurry.The present work, along with that similar one recently reported by the authors, is an unprecedented and relevant piece of research for the region.