外部性视角下的节水灌溉技术补偿标准核算——基于选择实验法

合理的补偿标准是节水灌溉技术补偿政策的核心,也是促进农户技术采用的关键内容。论文以石羊河下游民勤县为例,通过选择实验调研和RPL（Random Parameters Logit）模型估计,量化了节水灌溉技术采用的外部效益,并结合特定技术与农户谈判能力讨论了兼顾公平与效率的补偿标准。结果表明：民勤县城乡居民均希望实施节水灌溉技术来改善生态环境,技术采用的外部效益约为1 052.25元/hm²;以膜下滴灌技术为例,合理的补偿标准应在789.15元/hm²左右。从现行政策看,过低的补贴标准难以保障农户切身利益,导致政策响应不足。据此建议,完善成本收益核算体系,将技术采用的外部效益纳入补偿标准的核算中,提升补偿政策的公平性,同时也要根据技术类型及其采用面积进行精准化补偿,保障资金有效利用。     

奎屯高砷地下水灌溉区居民头发和指甲中砷含量研究

近十几年来,奎屯垦区高砷地下水被广泛用于农业灌溉,会在一定程度上降低改水措施对防治砷地方病的效果。为了解高砷地下水灌溉对居民体内砷累积的影响,选择头发和指甲作为评价指标,通过随机采集样品并用氢化物原子荧光光谱法测定样品中总As及As(Ⅲ)质量比的方式,对奎屯高砷地下水灌溉区居民砷污染健康影响现况进行了研究。结果表明,头发样品中总砷质量比为0.20~1.47μg/g(n=37),其中As(Ⅲ)质量比为0.06~0.67μg/g(n=32);51.35%的样品中总砷质量比高于卫生部标准(0.60μg/g),18.92%高于中国居民头发总砷正常值上限建议值(1.00μg/g),头发总砷质量比随居民居住年限和年龄增大而增大。指甲样品中总砷质量比为0.08~0.35μg/g(n=13),且与头发中总砷质量比呈正相关,当地居民体内呈现缓慢的As蓄积特征。改水30年后,奎屯垦区居民体内仍存在较高的砷水平,高砷地下水灌溉造成的人体健康风险不容忽视。     

沈阳市地铁疏干水的利用探析

针对沈阳市地铁疏干水利用的现状,综合考虑沈阳市的实际情况,总结出地铁疏干水利用的几种方法,主要包括作为运河、湖泊的补换水源,用于修复、重建湿地,农业灌溉用水以及作为水源热泵的水源等。提出沈阳市地铁疏干水利用的指导思想和法律保障。     

Biofilm structure and its influence on clogging in drip irrigation emitters distributing reclaimed wastewater

Using reclaimed wastewater for crop irrigation is a practical alternative to discharge wastewater treatment plant effluents into surface waters.However,biofouling has been identified as a major contributor to emitter clogging in drip irrigation systems distributing reclaimed wastewater.Little is known about the biofilm structure and its influence on clogging in the drip emitter flow path.This study was first to investigate the microbial characteristics of mature biofilms present in the emitters and the effect of flow path structures on the biofilm microbial communities.The analysis of biofilm matrix structure using a scanning electron microscopy (SEM) revealed that particles in the matrix of the biofilm coupled extracellular polysaccharides (EPS) and formed sediment in the emitter flow path.Analysis of biofilm mass including protein,polysaccharide and phospholipid fatty acids (PLFAs) showed that emitter flow path style influenced biofilm community structure and diversity.The correlations of biofilm biomass and discharge reduction after 360 h irrigation were computed and suggest that PFLAs provide the best correlation coefficient.Comparatively,the emitter with the unsymmetrical dentate structure and shorter flow path (Emitter C) had the best anti-clogging capability.By optimizing the dentate structure,the internal flow pattern within the flow path could be enhanced as an important method to control the biofilm within emitter flow path.This study established electron microscope techniques and biochemical microbial analysis methods that may provide a framework for future emitter biofilm studies.     

石家庄污灌区土壤重金属污染现状评价

为揭示污水灌溉对土壤环境质量的影响,本研究以石家庄市污灌区为例,对其表层土壤重金属Pb、Hg、Cr、Cd、As、Cu、Zn的含量进行了测定分析,按照单因子污染指数法和内梅罗综合污染指数法,根据土壤环境背景值标准进行了评价,并应用克里格插值方法对研究区内表层土壤污染的空间变异特征进行了分析。结果表明,研究区表层土壤中各重金属均有超过背景值现象;其中Cd含量远高于土壤背景值,为主要污染因子,Hg为次要污染因子,Cu、Cr、Pb、Zn基本上为轻度污染,As处于清洁状态;污染综合指数均大于1,处于轻度污染以上等级;各种金属单因子污染指数和综合指数在研究区的分布特点各不相同,总体上形成以东明渠、洨河主河道为中心逐渐向两边递减的污染分布状态,中度污染及严重污染将近占研究区总面积的一半以上。     

西藏地区春青稞耗水特征及适宜灌溉制度探讨

以中科院拉萨高原生态试验站为依托,通过开展春青稞生长与土壤水分定位观测实验,利用SHAW模型实现对春青稞农田蒸散发与土壤水深层渗漏与补给过程模拟,分析了春青稞的耗水特征,并对其适宜的灌溉制度进行了初步探讨:①春青稞生长期间,耗水450 mm左右,其中,分蘖—拔节、拔节—抽穗、抽穗—蜡熟这3个阶段是春青稞的耗水旺期,耗水量占整个生长期的72%。把握住该时期的水分供应,对提高作物产量十分重要。②在春青稞的需水关键期降水量仅能满足作物需水的58%,必须补充人工灌溉;但现行的灌溉制度由于灌溉量较大,不仅加大土壤蒸发,更造成较大的深层渗漏。③在播种—出苗、拔节—抽穗期分别灌溉50 mm,抽穗—蜡熟期灌溉60 mm,共减少灌溉用水125 mm后,深层渗漏减少了81%(131 mm);深层土壤水向上补给量增加了55%(44 mm)。节水灌溉不仅减少了土壤蒸发与深层渗漏也促使深层土壤水向上补给根系层,应该大力推广这一灌溉制度。     

灌溉管理改革的进展、特征及决定因素:黄河流域灌区的实证研究

论文采用两年的面板数据实证研究了我国黄河流域灌区灌溉管理改革的进展、特征及决定因素。研究结果表明,自20世纪90年代开始,黄河流域灌区灌溉管理改革取得了很大的进展,传统的集体管理已经逐步被承包管理和用水协会管理所取代,不同管理制度下农民参与的程度与管理的透明度都有所区别,政府的政策干预在促进灌溉管理改革上发挥了十分重要的作用,改革具有明显的政策导向性。在未来的灌溉管理改革中,政府部门应进一步出台相关鼓励改革政策,积极引导广大农民参与到改革的事业中,促进改革在更加广阔的农村地区的有效推进和良性发展。     

The Effects of Irrigation and Climate on the High Plains Aquifer: A County‐Level Econometric Analysis

The High Plains Aquifer (HPA) underlies parts of eight states and 208 counties in the central area of the United States (U.S.). This region produces more than 9% of U.S. crops sales and relies on the aquifer for irrigation. However, these withdrawals have diminished the stock of water in the aquifer. In this paper, we investigate the aggregate county‐level effect on the HPA of groundwater withdrawal for irrigation, of climate variables, and of energy price changes. We merge economic theory and hydrological characteristics to jointly estimate equations describing irrigation behavior and a generalized water balance equation for the HPA. Our simple water balance model predicts, at average values for irrigation and precipitation, an HPA‐wide average decrease in the groundwater table of 0.47 feet per year, compared to 0.48 feet per year observed on average across the HPA during this 1985–2005 period. The observed distribution and predicted change across counties is in the (?3.22, 1.59) and (?2.24, 0.60) feet per year range, respectively. The estimated impact of irrigation is to decrease the water table by an average of 1.24 feet per year, whereas rainfall recharges the level by an average of 0.76 feet per year. Relative to the past several decades, if groundwater use is unconstrained, groundwater depletion would increase 50% in a scenario where precipitation falls by 25% and the number of degree days above 36°C doubles. Editor’s note : This paper is part of the featured series on Optimizing Ogallala Aquifer Water Use to Sustain Food Systems. See the February 2019 issue for the introduction and background to the series.     

Simulating Soil Water Content,Evapotranspiration, and Yield of Variably Irrigated Grain Sorghum Using AquaCrop

Use of models to simulate crop production has become important in optimizing irrigation management in arid and semiarid regions. However, applicability and performance of these models differ across regions, due to differences in environmental and management factors. The AquaCrop model was used to simulate soil water content (SWC), evapotranspiration (ET), and yield for grain sorghum under different irrigation regimes and dryland conditions at two sites in Central and Southern High Plains. Prediction error (P_e), estimated as the difference between simulated and measured divided by measured, for SWC ranged from ?17% to 4% in fully irrigated, ?3% to ?10% in limited irrigated, and ?16% to 25% in dryland treatments. The P_e within ±4%, ?5%, and ?17% to 24% were attained for seasonal ET under fully irrigated, limited irrigated, and dryland conditions, respectively. P_e values for grain yield were within those previously reported and ranged from ?10% to 12%, ?12% to 7%, and 9% to 17% for fully irrigated, limited irrigated and dryland conditions, respectively. Overall performance of the AquaCrop model showed it could be used as an effective tool for evaluating the impacts of variable crop and irrigation managements on the production of grain sorghum in the study area. Finally, the application of the model in the study area revealed planting date has a significant impact on sorghum yield and irrigation requirements, but the impact of planting density was negligible. Editor's note : This paper is part of the featured series on Optimizing Ogallala Aquifer Water Use to Sustain Food Systems. See the February 2019 issue for the introduction and background to the series.     

Yield and Water Productivity of Winter Wheat under Various Irrigation Capacities

The Agricultural Production Systems sIMulator model validated in a prior study for winter wheat was used to simulate yield, aboveground crop biomass (BM), transpiration (T), and evapotranspiration under four irrigation capacities (ICs) (0, 1.7, 2.5, and 5 mm/day) with two nitrogen (N) application rates (N1, 94 kg N/ha; N2, 160 kg N/ha) to (1) understand the performance of winter wheat under different ICs and (2) develop crop water production function under various ICs and N rates. Evaluation was based on yield, aboveground crop BM, transpiration productivity (TP), crop water productivity (WP), and irrigation WP (IWP). Simulation results showed winter wheat yield increased with increase in N application rate and IC. However, the rate of yield increase gradually reduced with additional irrigation beyond 2.5 mm/day. A 5 mm/day IC required a total of 190 mm irrigation and produced a 5%–16% yield advantage over 2.5 mm/day. This indicates it is possible to reduce groundwater use for wheat by 50% incurring only 5%–16% yield loss relative to 5 mm/day. The TP and IWP for grain were slightly higher under IC of 1.7 mm/day (15.2–16.1 kg/ha/mm and 0.98–1.6 kg/m³) when compared to 5 mm/day (14.7–15.5 kg/ha/mm and 0.6–1.06 kg/m³), respectively. Since TP and IWPs are relatively higher under lower ICs, winter wheat could be a suitable crop under lower ICs in the region. Relationship between yield–T and yield–ET was linear with a slope of 15–16 and 9.5–10 kg/ha/mm, respectively. Editor's note : This paper is part of the featured series on Optimizing Ogallala Aquifer Water Use to Sustain Food Systems. See the February 2019 issue for the introduction and background to the series.