乌梁素海水环境容量分析

【目的】研究乌梁素海的水环境容量特征和探索水环境容量与入湖水质水量间的响应关系。【方法】采用零维模型分别计算并分析了乌梁素海冰封期与非冰封期的水环境容量,基于水文实际条件,分析入湖水量对出口断面污染物质量浓度的影响。【结果】冰封期湖泊的自净容量小于非冰封期时的自净容量,且冰封期的氮和有机物污染物的环境容量远小于非冰封期。【结论】非冰封期引入的黄河水和农田退水会导致湖泊氮磷水环境容量下降。有机物污染物的水环境稀释容量会因为黄河引水增加。     

The relative sensitivity to plant water stress during the reproductive phase of upland cotton (Gossypium hirsutum L.)

Summary The relative sensitivity of the cotton plant to water stress throughout the growing season was determined to identify when irrigation will have the greatest beneficial effect. Daily plant water stress for 72 different data sets of water applications was correlated to corresponding yield criteria. The magnitude of significant correlation was interpreted as the degree of sensitivity. Plant water stress during square formation and early flowering resulted in fewer bolls to reach maturity, but this detrimental effect was cancelled by the development of bigger bolls due to greater lint growth. This resulted in better seedcotton and lint yields. Flower and boll senescence which resulted from water stress during flowering peak, however, inhibited seedcotton and lint yields. The most pronounced inhibiting effect stress had on yields, was during boll development well after the end of effective flowering, when it inhibited boll development. Stress during ripening of the bolls increased lint and boll development and consequently enhanced yields. When limited quantities of water is available, preference should be given to irrigation during boll development, then by irrigation when the first flowers appear, followed by irrigation during peak flowering. Water should be withheld from opening of the first bolls.     

降雨对河流水质的不确定性影响研究

基于降雨对河流有机污染物稀释和降解的确定性数学模型,运用未确知数学中盲数等工具,对降雨期间的河流水质情况进行了研究。结果表明,由于降雨的影响,河流在丰水年丰水期的水质较枯水年枯水期得到明显的改善,自净能力得到很大的提高。同时,利用盲数运算方法得到了洋河3个断面对应不同可信度的COD浓度区间,其中对应最大可信度的COD浓度区间,可以为制定雨水对河道的清污作用方案提供理论依据。。     

Drought stress and alfalfa production in a mediterranean environment

Summary Plots with alfalfa (Medicago sativa L.) were exposed to water deficit during two consecutive summers. Drought stress treatments which lasted between 2 and 8 months during the first growing season had no carry-over effect on growth during the following winter and early spring of the subsequent year, compared with that observed in the fully irrigated plots. It was found that the capability of roots to extract water, and the rate of recovery from water stress after rewetting in autumn was independent of the duration of the drought. Water extraction varied curvilinearly with soil depth regardless of soil water content. Good agreement was found between an exponential model which was fitted to water extraction data in our experiment and data of root mass distribution taken from experiments conducted in the United States. This gives reasonable confidence in the prediction of the use of soil water reserves by plants under stress. A balance between saving of irrigation water and the expected loss of yield was determined. It is suggested that when water resources are limited in summer, irrigation of an established stand of alfalfa can be adjusted to water availability, without a decrease in water use efficiency.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 1762-E, 1986 series     

水资源不均等分配及其影响分析以簸箕李灌区为例

以簸箕李灌区为例,分析了该灌区水资源不均等分配及其所带来的对水资源利用方式和效率的影响。结果表明,在灌区内部从上游到下游,水资源可利用量很不均等,上游享用更多的水资源,地下水起到了调节水资源可用量年内波动的作用。上游地区地下水调节了春季水资源可用量的变异性,下游汛期储存的地下水在来年春季被重新利用,年平均利用量达到降雨灌溉总量的40.7%。下游农民应对水资源短缺的另2种途径是进行排水管理和减少种植面积,平均排水再利用量达到40 mm,因此下游地区具有更高的水资源利用效率。在水资源配置中应注意配置方案对水资源利用方式和效率的影响,同时要兼顾效率和公平。     

陕西沣河水环境特征及污染构成解析

通过资料收集和现场监测,对沣河2001-2011年水污染时空变化特征和成因进行了分析;在沣河秦渡镇水文站断面进行了洪水期与非洪水期水质水量同步监测,分析比较了洪水期和非洪水期水质特征;分别采用构建的水文分割法和通用的平均浓度法对沣河非点源污染负荷及其比重进行了计算。结果表明：（1）沣河2001～2006年污染较严重,2007～2011年水质逐年好转;2001～2006年从上游到下游沣河水质沿程逐渐恶化,2007～2011年沣河流域水质污染情况为上游<下游<中游;沣河2001～2006年NH3-N平均浓度基本处于Ⅲ类水质以内,2007～2011年基本处于II类水质以内;沣河2005~2006年COD平均浓度处于IV类水质以内,2007～2011年处于II类水质以内;洪水期水质好于非洪水期水质。（2）水文分割法和平均浓度法计算结果符合良好,该法可用于有限资料条件下非点源污染负荷的估算。沣河非点源污染影响在2007年后明显增大,2009年（P=45%）沣河秦渡镇水文站以上流域NH3-N和TN非点源污染负荷在总负荷中所占比例分别为47.40%和50.78%。NH3-N和TN年内非点源污染负荷所占比重从枯水期到丰水期呈明显递增趋势。     

Evapotranspiration,pan evaporation and soil water relationships for wheat (Triticum aestivum)

Controlled irrigation experiments were conducted for wheat grown in lysimeters having undisturbed soil profiles and protected from rainfall with transparent plexiglass roofs. Crop evapotranspiration during different crop growth stages and its relationships with Class A pan evaporation and soil water parameters were studied. The actual evapotranspiration during different crop growth stages was greatly influenced by amount and time of irrigation. The ratio of the maximum evapotranspiration and Class A pan evaporation increased linearly from germination to 46 days after sowing and remained constant at 1.45 from 46 to 76 days. Then the ratio decreased linearly towards the crop ripening. The actual evapotranspiration was equal to the maximum evapotranspiration up to the critical value of relative soil water, and then the actual evapotranspiration decreased at a very fast rate with further decrease in relative soil water. The critical value of the relative soil water varied from 0.65 to 0.84 during the crop growth-stage periods late tillering-heading and dough ripe-ripe, respectively.     

两种模型分析方法下冬小麦根系吸水深度的对比研究

为了研究冬小麦根系吸水深度,应用塑料管土柱法在田间进行冬小麦种植试验,测定了冬小麦越冬期、拔节期、抽穗期、灌浆期和成熟期不同土层深度土壤水稳定同位素值,并应用耦合模型和IsoSource多元线性模型对比分析了水源贡献率。结果表明,冬小麦在越冬期、返青期主要利用0~20 cm土层的土壤水,拔节期主要吸水深度为0~40 cm;抽穗期,基于耦合模型的主要吸水深度为0~40 cm,基于IsoSource多元线性模型的为0~40 cm和80~180 cm;灌浆期,基于耦合模型和IsoSource多元线性模型的主要不同吸水深度为180~200 cm,且基于耦合模型的该层贡献率明显高于IsoSource多元线性模型;成熟期主要利用0~40 cm和80~100 cm土层的土壤水,基于2种模型的分析结果相同。应用耦合模型求解贡献率,当分组较多且组间水稳定同位素差异较小时,应结合其他方法来保证其准确性。     

灌水对冬小麦耗水量和产量影响的试验研究

2006年10月~2008年5月在山西省运城灌溉试验站进行了两年的冬小麦需水量和灌溉制度试验研究。结果表明,冬小麦的耗水规律为播种~越冬阶段0.48~1.11 mm/d;越冬~返青阶段0.14~1.07 mm/d;返青~拔节阶段0.69~2.10 mm/d;拔节~抽穗阶段2.02~4.27 mm/d;抽穗~灌浆阶段达到最大值3.57~8.62 mm/d;灌浆~收获阶段1.63~3.85 mm/d。冬小麦耗水量与产量呈抛物线关系,为了取得高产和较高的水分利用率,全生育期的耗水量应在380~440 mm之间。在当地气候、土壤及栽培模式下,冬小麦的灌溉制度为全生育期灌水3次,灌水定额60~80 mm,灌溉定额180~240 mm。     

Farm-level and district efforts to improve water management during drought

The fifth year of drought in California brought reductions in surface water deliveries to many water districts. In the central San Joaquin Valley, water deliveries to Broadview Water District were reduced by 50% in 1990 and by 75% in 1991. The district increased the level of service provided to farmers during these years by providing accurate water use data, increasing the flexibility allowed in scheduling water deliveries, and managing water transfers and purchases when water was available. Farmers in the district implemented new irrigation practices and increased the efficiency of water applications. Several crops were irrigated more frequently than usual, but the amount of water applied during each irrigation event was reduced. The total amount applied during pre-irrigations and seasonal irrigations was also reduced. More than 38% of district land was idled in 1991, with the largest proportional reductions in melon, sugarbeet, and grain plantings. Field application efficiencies increased for all crops in 1990 and 1991 and the district-wide field application efficiency increased from 0.73 in 1989, to 0.77 in 1990, and 0.81 in 1991.     

Modeling the water budget in a deep caldera lake and its hydrologic assessment: Lake Ikeda, Japan

The hydrologic assessment of a lake water budget can be helpful in achieving proper water management and sustainable water use. A model to analyze a lake water budget was developed and verified for Lake Ikeda, Japan. Lake evaporation was estimated by numerical analyses of lake water temperature and the lake energy budget. Inflow from the lake catchment area and leakage from the lake bottom were estimated based on the tank model and Darcy's law, and the model parameters were optimized by the shuffled complex evolution method. The estimated monthly lake evaporation rate is consistent with the evaporation rate estimated by the energy budget Bowen ratio method based on in situ data from 2004 to 2005. Moreover, the calculated time series of daily lake levels agrees well with those of measured lake levels during 1983 to 1999. Thus, the model is useful for evaluating the lake water budget. Numerical analysis reveals seasonal and annual variation characteristics in the water budget components. Precipitation, inflow from the catchment area, and river water supply are generally high during the rainy season from June to July with substantial annual variation. Lake evaporation is greatest in October and least in April, but the annual variation is relatively small. Agricultural water use is relatively high from April to September. There are no marked seasonal changes in leakage and drinking water use. The lake level is generally highest in September and lowest in March, which is characterized by seasonal changes in water budget components. The model was also applied to 17-year simulations under hypothetical hydrologic conditions to examine the effect of water use and agricultural water management on the lake level. Results indicate that river water supply, provided under the agricultural water management system, effectively compensates for the decrease in lake water resulting from agricultural water use.     

Sprinkler water distributions as affected by winter wheat canopy

Sprinkler uniformity is often used to evaluate irrigation system performance. The measurement of uniformity is generally made from one test when no crop is present. However, a developing crop canopy has significant potential to modify the distribution of water applied during irrigation. This study was conducted to evaluate the influence of a winter wheat canopy on sprinkler uniformity and on canopy-intercepted water by measuring water distributions above and below the canopy. The Christiansen uniformity coefficient (CU) was calculated on both a daily and a cumulative basis. The CU was higher below the canopy than above the canopy. Canopy-intercepted water, which is here defined as the sum of canopy storage and stemflow, increased with increasing water application depth. Sprinkler uniformity had no significant effect on the mean amount of water interception by the canopy. The ratio of water interception to total water application depth for the whole irrigation season was between 0.24 and 0.28. The CUs calculated from the cumulative depth caught above and below the canopy are larger than the averages of individual CU values during the irrigation season. Measurement of individual CUs during the irrigation season therefore underestimates the cumulative CU. Experimental results also demonstrated that sprinkler uniformity in this study had little effect on crop yield. Received: 1 February 2000     

Conjunctive use of saline and non-saline irrigation waters in semi-arid regions

In arid and semi-arid regions, effluent from sub-surface drainage systems is often saline and during the dry season its disposal poses an environmental problem. A field experiment was conducted from 1989 to 1992 using saline drainage water (EC=10.5–15.0 dS/m) together with fresh canal water (EC=0.4 dS/m) for irrigation during the dry winter season. The aim was to find if crop production would still be feasible and soil salinity would not be increased unacceptably by this practice. The experimental crops were a winter crop, wheat, and pearl-millet and sorghum, the rainy season crops, grown on a sandy loam soil. All crops were given a pre-plant irrigation with fresh canal water. Subsequently, the wheat crop was irrigated four times with different sequences of saline drainage water and canal water. The rainy season crops received no further irrigation as they were rainfed. Taking the wheat yield obtained with fresh canal water as the potential value (100%), the mean relative yield of wheat irrigated with only saline drainage water was 74%. Substitution of canal water at first post-plant irrigation and applying thereafter only saline drainage water, increased the yield to 84%. Cyclic irrigations with canal and drainage water in different treatments resulted in yields of 88% to 94% of the potential. Pearl-millet and sorghum yields decreased significantly where 3 or 4 post-plant irrigations were applied with saline drainage water to previous wheat crop, but cyclic irrigations did not cause yield reduction. The high salinity and sodicity of the drainage water increased the soil salinity and sodicity in the soil profile during the winter season, but these hazards were eliminated by the sub-surface drainage system during the ensuing monsoon periods. The results obtained provide a promising option for the use of poor quality drainage water in conjunction with fresh canal water without undue yield reduction and soil degradation. This will save the scarce canal water, reduce the drainage water disposal needs and associated environmental problems.     

Estimation of local and regional components of drain-flow from an irrigated field

The contribution of regional ground water and deep percolation from a furrow irrigated field to total drain flow was estimated using salt load analysis. It was found that 64% of the drain flow comes from regional ground water flow. The electrical conductivity of the drain water was highly correlated with the drain flow rate. From the field water balance with deep percolation as estimated from the salt load analysis, using yield function derived evapotranspiration, and measured changes in root zone water storage, it was shown that 14% of the crop evapotranspiration comes from ground water during the study period.     

Simulation of heat and water transfer in a surface irrigated, cropped sandy soil

Field experiments were conducted to validate a one-dimensional numerical Simple Soil Plant Atmospheric Transfer (SiSPAT) model that simulates heat and water transfer through the root zone of a surface irrigated, cropped sandy soil. The model accounts for the dominant processes involved in water and heat transfer in a cropped soil. Model validation used field experimental data from 2004 and suggested that the SiSPAT model could be successfully applied to predict soil water and temperature dynamics of a cropped soil in experimental conditions. Validation resulted in high values of model efficiency (ME), and low values of root mean square deviation (RMSD) and mean bias error (MBE) between the simulated and measured values. Model predictions were obtained using field experimental data from 2005 and showed that the SiSPAT model reproduced reasonably well the experimental distributions of soil moisture and temperature. Minor discrepancies between the predicted and measured data during the prediction period can probably be attributed to the uncertainties in soil water content and soil temperature probe measurements. In addition, the influence of irrigation water temperature on water and heat transfer was ignored in the model. This could have contributed to deviations between the simulated and measured values during the experiment. Prediction results indicated that the variability of the water and heat transfer fluxes following a surface irrigation in different stages of the crop (wheat) growth season resulted from the difference in net radiation reaching the cropped soil due to the varying shielding factor as controlled by leaf area index (LAI), root water uptake, meteorological conditions and soil water regime. Furthermore, an interaction between water and heat transfer through the root zone in the cropped soil could be observed during the prediction period.     

设施滴灌无土栽培红掌耗水规律研究

以连栋日光温室内无土盆栽红掌为试材,根据控制灌水下限占田间持水率90％、80％、70％、60％和50％的比例设置5个处理,系统研究了滴灌条件下气象因子对红掌耗水规律的影响,探讨了Penman-Monteith模型对设施无土栽培红掌耗水的预测。结果表明,供试条件下红掌日耗水量分阶段结果为：移栽至8月中旬0．2～0．4mm...     

Scheduling the cropping calendar in wet-seeded rice schemes in Malaysia

The Besut Irrigation Scheme, Terengganu, Malaysia is one of the eight gazetted main rice-growing areas in Malaysia. These eight granaries are targeted to produce only 65% of the total rice requirements of the nation. This scheme faces water scarcity especially during the off-season with the present existing cropping schedule. This study discusses the ways and means to overcome the water scarcity problem by setting the calendar for cropping schedules taking into consideration rainfall, river flow available and irrigation water requirements. A water balance approach using 48 years of rainfall and weather data was pursued in this study. The present main season from land preparation to crop harvest lasts from 1st November to 6th April, with land preparation being carried out during the heaviest rains in early November. However, the heavier rains may result in the postponement of seeding. Delays in crop planting during this main season can result in the cancellation of the following off-season crop from May to October. Shifting the land preparation works from November 1 to an earlier date, September 15, would result in a better match of crop water needs with the prevailing rainfall season (normally most of the rainfall occurs between September and December). This proposed schedule (15th September–10th February) also increases the probability that land preparation and subsequent seeding can be done for a second crop in the revised off-season period, 15th March–10th August. The present off-season schedule is from 5th May to 7th October and water scarcity during the vegetative and reproductive phases of the crop growth can be a problem. With the shifting of the off-season to start on March 15, severe water shortage can be avoided. The proposed revised cropping schedules could reduce the irrigation water requirements for the main season and off-season by 30% (equivalent to 60 mm of water) and 19% (equivalent to 37 mm of water), respectively.     

Seasonal variations in nitrate leaching in structured clay soils under mixed land use

Nitrate leaching was studied for 2 years in a structured clay soil (Evesham series) under grass, winter wheat and spring barley at N fertilizer inputs of 135–144 kg ha^?1 year^?1. Measurements of soil water to 2 m depth by neutron probe showed that the year could be divided into well defined periods of deficit, separated by a period when the soil was at its winter mean water content. Soil water potentials showed very little gradient for water flow below 1 m, and a persistent convergent zero flux plane at 40–60 cm depth during the autumn wetting-up period (September—November).Nitrate concentration in the drainage increased with discharge rates up to 3–6 mm day^?1. Mean nitrate concentrations were generally highest during intermittent drain-flow in the autumn. Of the total N leached over the 2 years, 23 to 28% (5–7 kg N ha^?1) was lost during this period. The remainder (13–25 kg N ha^?1) was leached during winter and virtually no N was lost in the following spring-early summer. This seasonal pattern of N leaching was interpreted in terms of intermittent flow during rainfall of nitrate-rich water from surface layers, which bypassed the relatively dry soil matrix at 40–60 cm, but was intercepted by natural and artificial drainage channels. Implications for the prediction of N leaching loss based on the concept of excess winter rainfall are discussed. When predicting the start of N leaching in structured clay soils, the soil water status should be assessed from measurements of water potential rather than water content.     

Effect of water deficit in different growth stages on stem sap flux of greenhouse grown pear-jujube tree

The effects of water deficit in different fruit growth stages on the variation of stem sap flux of 6-year old greenhouse-grown pear-jujube trees were investigated. Treatments included sufficient water supply during the whole fruit-growing period (T₁), mild water deficit during the flowering–fruit setting stage (T₂), moderate water deficit during the fruit rapid growth stage (T₃) and severe water deficit during the fruit maturing stage (T₄). Results showed that significant compensation effect on stem sap flux after re-watering was observed in T₂, but not in T₃ and T₄ stages. At the end of rapid growth stage, the diurnal variation of stomatal conductance generally had a similar trend as that of stem sap flux, but with a distinct midday depression from 12:00 to 14:00 p.m. In addition, a linear relationship between the relative available soil water content (RAWC) and the ratio of daily stem sap flux to that of sufficient water treatment was observed (R² = 0.4489).     

宁夏石嘴山市潜水的灌溉水质评价与水资源合理利用

石嘴山市水资源的合理利用包括潜水资源、引黄(河)渠水资源、灌溉期间排水沟水资源以及贺兰山东麓沟谷水资源的合理利用。其中,潜水资源的利用是石嘴山市水资源合埋利用的核心。本文通过大面积的水质评价,给出了可供利用的潜水面积;阐述了不同水资源合埋利用的途径;估算了合埋利用潜水资源和引黄水资源的节水潜力。本文采用的方法和阐述的观点对我国西北及内蒙河套灌区有一定的参考价值。