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1.
《中国农村水利水电》2020,(7)
县域水环境承载力评价是我国水污染防治行动计划的目标要求之一,是实现区域水环境差异化、科学化管理和排污许可分配技术的重要基础。以位于太湖西南岸河网片区的浙江省长兴县为例,基于水生态功能区划分的结果,构建了包括水资源、水环境、水生态、土地生态功能4类14个指标组成的水环境承载力指标体系,并确定了各指标权重,进而利用向量模法对分区水环境承载状态进行综合评价。结果表明:长兴县水环境承载力整体上处于中等偏下水平,区域差异明显,D_1和D_4分区承载力值分别为0.062、0.029;水资源指数和土地生态功能指数总体表现较好,水环境、水生态指数整体表现较差。研究显示,河道水生态退化、水功能区水质不达标以及点、面源污染等是制约长兴县水环境承载力的主要因素,也是提升长兴县水环境承载力的关键。 相似文献
2.
针对太湖流域近年来城市化带来的城市河网水体滞留、水环境恶化问题,探究活水对流域水体流动性和水环境的改善效果。选取太湖流域锡澄片主城区为典型区域,构建一维非稳态水动力水质耦合模型,拟定了多种沿江枢纽和相关内河闸站配合的方案,探究活水对太湖流域平原河网的影响,定量评估不同水平的活水方案对研究区水体流动性和水环境的改善效果。结果表明,配置合理的活水方案可有效改善主城区河道的流动性及水环境;超过一定水量后,随着流量的增加,河道水质改善效果的提升很小。 相似文献
3.
通过周期性换水更新城市湖泊水质的解析模型 总被引：3，自引：0，他引：3
基于具有周边环境连续输入的充分混合的反应器原理及一些简化假设,提出了借助周期性地引排换水改善城市湖泊水质的数学模型,导出了城市湖泊中污染物平均浓度和水质改善指标的解析表达式。模型包含了污染物综合降解系数、引排换水周期、湖泊中原来的水质、引入水的水质、湖泊承受的污染负荷以及引排历程等各项影响因素。并证明了在一定的条件下,坚持周期性的引排操作将使湖泊水质及水质改善指标趋向稳定。模型可用于城市湖泊水环境治理的规划设计,亦可为此种治理工程运行参考。 相似文献
4.
《中国农村水利水电》2019,(5)
以泾河流域为例,通过对该流域2014-2016年各季节水质与水生态环境指标的提取与测定,构建了能够反映流域水环境整体状况的指标体系和分级标准;然后利用MATLAB语言建立了L-M优化改进的BP网络结构,并科学、准确地评价了泾河流域水环境承载力状况。研究表明:L-M算法不仅克服了经典BP网络训练速度慢、局部陷入极小的缺陷,而且可提高输出结果的有效性与准确性;泾河流域2014-2016年的水环境承载力分别为0.67、0.52、0.48,整体处于基本可承载水平,并表现出逐渐下降的趋势。 相似文献
5.
为了定量分析人口增长、经济发展、资源短缺和环境污染等因素对流域水环境的综合影响,对赣江流域水环境承载能力进行评价。根据水环境承载力的基本概念,选取适当的水资源和水质量承载力指标,运用指标体系评价法分别计算2006—2010年赣江水环境承载力。结果表明,流域人口、灌溉面积的承载度最大值达到0.90和0.96,均有超过水环境承载力的趋势;GDP承载度最大值为0.38,仍有较大的发展空间。富营养化指标TN均大于1,一直处于负荷承载;TP五年平均承载度为0.9,有超过承载力的趋势;COD的承载度在0.3周围波动,较为良好。赣江流域水环境承载力为负承载,水质量承载力影响程度更大。 相似文献
6.
7.
湖北省江汉平原汉江以北的浅丘水网区随着地区经济社会迅速发展,入河污染负荷日益增多,加上浅丘水网区水体流动性差,区域内河湖水环境质量不容乐观,主要河湖水体水质基本处于Ⅳ类到劣Ⅴ类。从水环境改善角度出发,将一江三河水网区众多河湖划分为骨干河流、小支流、城市湖泊、农村湖泊四类基本单位,并以此为基础构建了一江三河水网区多单元多流域生态环境需水耦合模型,分析了模型构建关键技术,从系统角度研究一江三河水网区以改善水环境质量为目标的生态环境需水。 相似文献
8.
淮河流域水环境承载力评价研究 总被引：3，自引：0，他引：3
以淮河流域为研究对象,基于水环境承载力理论的内涵,设计并构建了淮河流域水环境承载力评价指标体系,应用变量模法对淮河流域的水环境承载力水平进行了评价,并分析了不同年份淮河流域水环境承载力评价值的变化趋势。结果表明,1999年—2010年淮河流域的水环境承载力呈不断增长的趋势,其承载力水平值处在0.01～0.06之间,水环境承载力水平较低。研究成果为淮河流域各地区科学制定措施,以提高水环境承载力,实现可持续发展战略提供了科学的理论依据和技术支持。 相似文献
9.
10.
郑州市水环境承载力研究 总被引：2，自引：0，他引：2
采用系统动力学模型和控制目标反推模型（COIM）研究了郑州市水环境承载力状况。以Vensim为工具软件,建立了系统动力学模型,选取了5个指标并利用向量模法对不同发展方案进行评价。结果表明,综合方案全面考虑南水北调工程调水、水资源合理开发与污水治理,既增加了水资源的供应量,又提高了水体的质量,较大幅度提高了郑州市水环境承载力,且未来规划水平年水环境承载力呈上升趋势。然而,系统动力学评价结果只是一个比值,只能从整体上反映水环境承载力的发展趋势。在此基础上,运用COIM模型,以水体COD为控制目标对郑州市的水环境承载力情况进行分析,并给出了提高水环境承载力的多种对比方案。综合分析表明,系统动力学模型可较好地把握水环境承载力的整体发展趋向, 有利于宏观对策的提出;控制目标反推模型可较好地反映不同措施下的水环境状况,有利于具体措施的提出。 相似文献
11.
Stanley Yokwe 《Agricultural Water Management》2009,96(8):1223-1228
This study investigates the productivity and value of water in two smallholder irrigation schemes (Zanyokwe and Thabina) in South Africa. We apply the residual valuation method (RVM), willingness to pay (WTP) and cost-based approaches (CBA) (i.e. accounting costs of operation and maintenance) to evaluate water productivity and values per crop, per farm, and by scheme. In both schemes, water value estimated by the RVM for vegetables (cabbage, tomatoes and butternuts) is greater than water value for dry maize. At the farm and scheme levels, a comparison was made between gross margin per m3 of water, WTP per m3 and accounting cost per m3 to estimate the relative value of water productivity. The active farmers in the Zanyokwe scheme have lower WTP per m3 (R0.03) than the gross margin of output (R0.69). Also, the accounting cost (R0.084) per m3 of water is less than the gross margin. In the Thabina scheme, active farmers are willing to pay (R0.19) per m3 of water. Hence farmers in Thabina are ready to pay as much as three times the proposed costs of O&M (R0.062) per m3 of water used. Both the accounting cost and willingness to pay are less than the gross margin per m3 of water in the Zanyokwe scheme. Our findings indicate that extension and training may be required to improve the productive use of water for those farmers whose returns are insufficient to cover the cost of supply. 相似文献
12.
Baozhong Zhang Shaozhong Kang Fusheng Li Taisheng Du 《Agricultural Water Management》2010,97(11):1898-797
Grapevines are extensively grown in the arid region of China, but little information is available on the diurnal, seasonal and interannual variability of vineyard evapotranspiration (ET). To address this question, two vineyards in the arid region of northwest China were taken as an example to study the variation of ET using Bowen ratio-energy balance method in 2005-2008. Results indicate that the Bowen ratio method provided accurate estimate of vineyard ET as the instrument was correctly installed. Irrigation and rainfall increased daily ET by 38 and 175%, respectively, but frost decreased it by 32%. Daily ET had a maximum value of 1.6-3.5 mm/d at the berry development stage, and a minimum value of 0.8-1.7 mm/d at the early and later stages. The total ET was 226-399 mm over the growing season. The ratio of transpiration to evapotranspiration was 0.52 and the modified crop coefficient (Kcm) was 0.71-0.88 (except 2005) over the whole growing stage. Larger interannual difference of ET and Kcm mainly resulted from the difference of irrigation and rainfall between different years. 相似文献
13.
Effects of salinity on fruit yield and quality of tomato grown in soil-less culture in greenhouses in Mediterranean climatic conditions 总被引：2，自引：0，他引：2
There is increasing pressure to reduce water use and environmental impact associated with open system, soil-less production in simple, plastic greenhouses on the Mediterranean coast. This may force the adoption of re-circulation of nutrient solutions. In south-eastern Spain, irrigation water is mostly from aquifers and has moderate levels of salinity. The adoption of re-circulation using moderately saline water requires detailed information of crop response to salinity, in order to optimise management. The effect of salinity on fruit yield, yield components and fruit quality of tomato grown in soil-less culture in plastic greenhouses in Mediterranean climate conditions was evaluated. Two spring growing periods (experiments 1 and 2) and one long season, autumn to spring growing period (experiment 3) studies were conducted. Two cultivars, ‘Daniela’ (experiment 1) and ‘Boludo’ (experiments 2 and 3), were used. Seven levels of electrical conductivity (EC) in the nutrient solution were compared in experiment 1 (2.5–8.0 dS m−1) and five levels in experiments 2 and 3 (2.5–8.5 dS m−1). Total and marketable yield decreased linearly with increasing salinity above a threshold EC value (ECt). There were only small effects of climate and cultivar on the ECt value for yield. Average threshold EC values for total and marketable fruit yield were, respectively, 3.2 and 3.3 dS m−1. The linear reductions of total and marketable yield with EC above ECt showed significant differences between experiments, the slope varying from 7.2% (autumn to spring period, ‘Boludo’) to 9.9% (spring period, ‘Boludo’) decreases per dS m−1 increase in EC for total yield, and from 8.1% (spring period, ‘Daniela’) to 11.8% (spring period, ‘Boludo’) for marketable yield. The decrease of fresh fruit yield with salinity was mostly due to a linear decrease of the fruit weight of 6.1% per dS m−1 from an ECt of 3.0 dS m−1 for marketable fruits. Reduction in fruit number with salinity made a smaller relative contribution to reduced yield. Blossom-end rot (BER) increased with increasing salinity. There was a higher incidence of BER with spring grown crops, and ‘Boludo’ was more sensitive than ‘Daniela’. Increasing salinity improved various aspects of fruit quality, such as: (i) proportion of ‘Extra’ fruits (high visual quality), (ii) soluble solids content, and (iii) titratable acidity content. However, salinity decreased fruit size, which is a major determinant of price. An economic analysis indicated that the EC threshold value above which the value of fruit production decreased linearly with increasing salinity was 3.3 dS m−1, which was the same as that for marketable yield. In the economic analysis, the value of increased visual fruit quality was offset by reduced yield and smaller fruit size. 相似文献
14.
Grapevines are extensively grown in the semiarid and arid regions, but little information is available on the variability of energy partitioning and resistance parameters for the vineyard. To address this question, an eddy covariance system was applied to measure energy balance over a vineyard in northwest China during 2005-2006. Result indicated that 2-year average Bowen ratio (β) of vineyard was 1.0, canopy resistance (rc) 289.3 s m−1, aerodynamic resistance (ra) 9.7 s m−1 and climatological resistance (ri) 117 s m−1. This implied that the annual energy was split almost equally between sensible heat and latent heat. Compared to the corresponding values in other ecosystems reported by Wilson et al. [Wilson, K.B., Baldocchi, D.D., Aubinet, M., Berbigier, P., Bernhofer, C., Dolman, H., Falge, E., Field, C., Goldstein, A., Granier, A., Grelle, A., Halldor, T., Hollinger, D., Katul, G., Law, B.E., Lindroth, A., Meyers, T., Moncrieff, J., Monson, R., Oechel, W., Tenhunen, J., Valentini, R., Verma, S., Vesala, T., Wofsy, S., 2002. Energy partitioning between latent and sensible heat flux during the warm season at FLUXNET sites. Water Resource Research 38, 1294-1305.], the vineyard had a higher β, rc and ri than deciduous forests, corn and soybean, and grassland. Such difference was mainly attributed to (1) serious water stress in 2005, which resulted in a greater rc up to 364.4 s m−1; (2) sparse canopy with row spacing of 2.9 m and plant spacing of 1.8 m; (3) warm-dry climate and high attitude (1581 m) along with higher ri and lower psychrometer (54 Pa K−1) in the arid region of northwest China. These characters of vineyard revealed varying process of energy partitioning and surface resistance, and provided a scientific basis in understanding and modeling water and energy balance for the vineyard in the semiarid and arid regions. 相似文献
15.
Northeast Thailand has a semi-humid tropical climate which is characterized by dry and rainy seasons. In order to stabilize crop production, it may be necessary to develop new water resources, such as soil moisture and groundwater, instead of rainfed resources. This is because rainfed agriculture has already been unsuccessfully tried in many areas of this region. In this study, we investigate the soil water content in rainfed fields in Khon Kaen in Northeast Thailand, where rice and sugarcane were planted, over a 1-year period that contained both dry and rainy seasons, and estimate the actual evapotranspiration (ETa) using micrometeorological data. In addition, we assess the water balance from the results of the soil water content investigation and the actual evapotranspiration. Although the soil water content at depths above 0.6 m in both the lower and the sloping fields gradually decreased during the dry season, the soil water content at a depth of 1.0 m was under almost constant wet conditions. Two-dimensional profiles of the soil water content demonstrated that at the end of the dry season, the soil layers below a depth of 0.4 m showed a soil water content of more than 0.10-0.15 m3 m−3, thus suggesting that water was supplied to the sugarcane from those layers. The range in ETa rates was almost the same as that in the previous study. The average ETa rates were 3.7 mm d−1 for the lower field and 4.2 mm d−1 for the sloping field. In the dry season, an upward water flow of 373 mm (equivalent to a flux of 1.9 mm d−1) was estimated from outside the profile. The source of this upward water flow was the sandy clay (SC) layer below a depth of 1 m. It was this soil water supply from the SC layer that allowed the sugarcane to grow without irrigation. 相似文献
16.
Excess phosphorus (P) in freshwater systems has been associated with eutrophication in agro-ecosystems of the US Midwest and elsewhere. A better understanding of processes regulating both soluble reactive phosphorus (SRP) and total phosphorus (TP) exports to tile-drains is therefore critical to minimize P losses to streams while maintaining crop yield. This paper investigates SRP and TP dynamics at a high temporal resolution during four spring storms in two tile-drains in the US Midwest. Depending on the storm, median concentrations varied between 0.006-0.025 mg/L for SRP and 0.057-0.176 mg/L for TP. For large storms (>6 cm bulk precipitation), for which macropore flow represented between 43 and 50% of total tile-drain flow, SRP transport to tile-drains was primarily regulated by macropore flow. For smaller tile-flow generating events (<3 cm bulk precipitation), for which macropore flow only accounted for 11-17% of total tile-drain flow, SRP transport was primarily regulated by matrix flow. Total P transport to tile-drains was primarily regulated by macropore flow regardless of the storm. Soluble reactive P (0.01-1.83 mg m−2/storm) and TP (0.10-8.64 mg m−2/storm) export rates were extremely variable and positively significantly correlated to both mean discharge and bulk precipitation. Soluble reactive P accounted for 9.9-15.5% of TP fluxes for small tile-flow generating events (<3 cm bulk precipitation) and for 16.2-22.0% of TP fluxes for large precipitation events (>6 cm bulk precipitation). Although significant variations in tile-flow response to precipitation were observed, no significant differences in SRP and TP concentrations were observed between adjacent tile-drains. Results stress the dominance of particulate P and the importance of macropore flow in P transport to tile-drains in the US Midwest. Although only spring storms are investigated, this study brings critical insight into P dynamics in tile-drains at a critical time of the year for water quality management. 相似文献
17.
Applying high rates of nitrogen (N) fertilizer to crops has two major disadvantages: (1) the low N fertilizer use efficiency and (2) the loss of N by leaching, which may cause groundwater nitrate (NO3−) pollution, especially in humid areas.The objectives of this study were to adjust and validate the LEACH-W model simulations with data observed in the field; to quantify nitrate concentrations in the soil solution; to estimate N loss by leaching; and to determine the moments during the year when greatest nitrate transport events occur beyond the rooting profile.A randomized complete block design with four replications was established on a typic Argiudoll. Crop fertilization treatments consisted of three N rates (0, 100, and 200 kg N ha−1) using urea and ammonium nitrate solution (UAN) as the N source. Corn (Zea mays L.) was planted and ceramic soil-water suction samplers were installed to depths of 1, 1.5 and 2 m. Drainage was estimated by the LEACH-W model, which adjusted very well the actual volume of water in the soil profile. Nitrogen losses were statistically analyzed as repeated measure data, using the PROC MIXED procedure.Losses of nitrate-nitrogen (NO3−-N) during the study increased as the rate of N applied increased. At all depths studied, statistically significant higher values were found for 200 N compared to 100 N and 0 N, and for 100 N compared to 0 N (p < 0.001).The greatest NO3−-N losses through leaching occurred during crop growth. Significant differences (p < 0.05) were found between cropping and fallow in the three treatments and depths studied for seasons 4 and 5; these two seasons produced the highest drainage volumes at all depths. 相似文献
18.
This paper evaluates the performance of the first drip irrigation scheme in commercial tea production in Tanzania with a view
to making recommendations for improved management and providing data for investment decisions. Uniformity, efficiency and
adequacy of irrigation were calculated and the scheduling of irrigation water was reviewed. Operators were interviewed to
highlight the main benefits and problems of the system. Investment and recurrent costs of drip and overhead sprinkler systems
were quantified and compared. Root development was assessed qualitatively using excavation pits. Irrigation uniformity DU and efficiency ranged between 88 and 95% in the 10 out of 14 irrigation blocks where endline pressures were at least 0.5
bars, and between 77 and 89% in the four blocks were endline pressure was less than 0.5 bars. Scheduling drip irrigation using
tensiometers offered potential water savings of 26% in comparison to a water balance schedule, but these are not currently
realised. Gross marginal income was very sensitive to tea price and yield. Economically optimal fertilizer rates vary in dependence
of tea price and yield and appear to be lower than the current level of 300 kg N ha−1. The higher costs under drip, compared to overhead sprinklers, were mainly for purchase and installation and fertilizer.
The costs of labour for applying water and fertilizer were reduced by nearly 50%. At average 2002 tea prices of 1.31 US$ kg−1, drip irrigation would improve the grower’s gross margin if an additional yield of at least 411 kg ha−1 was achieved. The main threats to drip system performance are discussed. Future research efforts should aim at establishing
the yield response of tea to water and fertilizer under drip irrigation. 相似文献
19.
Furrow diking in conservation tillage 总被引：2，自引：0，他引：2
Crop production in the Southeastern U.S. can be limited by water; thus, supplemental irrigation is needed to sustain profitable crop production. Increased water capture would efficiently improve water use and reduce supplemental irrigation amounts/costs, thus improving producer's profit margin. We quantified infiltration (INF), runoff (R), and sediment (E) losses from furrow diked (+DT) and non-furrow diked (−DT) tilled conventional (CT) and strip tillage (ST) systems. In 2008, a field study (Tifton loamy sand, Typic Kandiudult) was established with DT, ST, and CT systems. In 2009, a field study (Faceville loamy sand, Typic Kandiudult) was established with DT and ST systems. Treatments (6) included: CT − DT, CT + DT, ST1 (1-year old) − DT, ST1 + DT, ST10 (10-year old) − DT, and ST10 + DT. Simulated rainfall (50 mm h−1 for 1 h) was applied to each 2-m × 3-m plots (n = 3). Runoff and E were measured from each 6-m2 plot. ST1 + DT plots had 80-88% less R than ST1 − DT plots. Any disturbance associated with DT in ST1 systems did not negatively impact E values. For both soils, CT − DT plots represented the worst-case scenario in terms of measured R and E; ST + DT plots represented the best-case scenario. Trends for R, E, and estimated plant available water (PAW) values decreased in order of CT − DT, CT + DT, ST1 − DT, ST1 + DT, ST10 − DT, and ST10 + DT treatments. From a hydrology standpoint, ST1 − DT plots behaved more similarly to CT plots than to other ST plots; from a sediment standpoint, ST1 − DT plots behaved more similarly to other ST plots than to CT plots. DT had no effect on ST10 plots. CT − DT and ST10 + DT plots resulted in 5.9 (worst-case) and 8.1 (best-case) days of water for crop use, a difference of 2.2 days of water for crop use or 37%. Compared to the CT − DT treatment, an agricultural field managed to CT + DT, ST1 − DT, ST1 + DT, ST10 − DT, and ST10 + DT would save a producer farming the CT − DT field $5.30, $9.42, $13.55, $14.14, and $14.14 ha−1, respectively, to pump the amount of water lost to R and not saved as INF back onto the field. The most water/cost savings occurred for CT and ST1 plots as a result of DT. Savings for CT + DT, ST1 − DT, and ST1 + DT treatments represent 27%, 47%, and 68% of the cost of DT ($20 ha−1) and 37%, 67%, and 96% of the savings a producer would have if managing the field to ST for 10 years without DT (ST10 − DT) in a single 50-mm rainfall event. For row-crop producers in the Southeastern U.S. with runoff producing rainfall events during the crop growing season, DT is a management practice that is cost-effective from a natural resource and financial standpoint for those producers that continue to use CT systems and especially those that have recently adopted ST systems into their farming operations. 相似文献
20.
Nitrogen and phosphorous concentrations in runoff from a purple soil in an agricultural watershed 总被引：3，自引：0，他引：3
Nutrient loss from purple soils has been reported to increase pollution of the Yangtze River. However, few studies have addressed the variations of nutrient concentration in runoff during natural rainstorms in the regions. Nitrogen and phosphorus concentrations in runoff waters from a small agricultural watershed, in the purple soil region of southwest China, were investigated for four natural rainstorms occurred in a conventional double cropping system (wheat-corn) and another six rainstorms in a new triple cropping system (wheat-corn-sweet potato). The NO3− concentrations in runoff for the observed rainstorms generally varied from 1.0 to 3.5 g m−3, which were noticeably affected by flow rates. A significant logarithmic correlation between NO3− concentrations and flow rates for each rainstorm was identified. In contrast, the concentrations of NH4+ and dissolved reactive phosphorus (DRP) in runoff fluctuated substantially without a noticeable trend for each rainstorm. Positive linear correlation between the concentrations of DRP and sediment for each rainstorm tested was found under the circumstances of double cropping system. In addition, the ratios of NO3− to NH4+ for the loss amount in 10 rainstorms varied from 1 to 7 for the triple cropping system and 16-29 for the double cropping system. Furthermore, the ratios of the sum of NO3− and NH4+ to DRP for the loss amount in 10 rainstorms ranged from 12 to 79 depending on the cropping systems. Nitrate nitrogen was proved to be the main form of inorganic nitrogen loss in runoff water in the purple soil region. Compared with the conventional double cropping system, the new triple cropping system tends to cause more NH4+ loss. These findings would help develop the effective erosion control strategies and select a suitable cropping system to reduce potential pollution hazards. 相似文献