GS环境下基于DEM的流域分析

随着流域数字化进程中空间基础数据库的建设，应用地理信息系统平台有效地分析流域和水库的基本水文信息成为可能。结合在长江一级支流黄柏河流域分布水文模型建立过程中对DEM数据的应用，重点论述了从栅格DEM数据中提取水文信息的基本方法、研究进展、河网提取过程中临界支撑面积的确定方法、DEM数据分辨率对于水文要素提取的影响及其最小分辨率的确定方法。     

微灌用网式过滤器局部水头损失的

在对网式过滤器进行了系统的水力性能试验基础上，分析了堵塞对过滤器局部水头损失的影响，指出过滤器的局部水头损失变化与过滤流量、过滤时间、水源含沙量有关，这些因素主要决定了过滤元件堵塞程度和变化快慢，即有效过水面积减小的频率，从而决定了额外局部水头损失增加的快慢程度。并提出了在含沙水条件下计算局部水头损失的经验关系式，指出过滤器在实际运用中，应保证压降曲线不发生急剧上升，并可以根据不同水质条件，确定其冲洗时的压差允许值和冲洗间隔时间。     

不同灌排模式稻田排水中氮磷流失规律

为了研究不同灌排模式稻田排水中氯磷流失规律,以集成合理的节水灌溉与控制排水技术,在江苏高邮开展田间试验.试验区排水斗沟出口处设水位调控闸门,在水稻不同生育阶段对排水沟水位及田间水分进行控制,形成新型的控制灌排模式.与常规灌排模式进行对比,两年田间试验成果表明,控制灌排模式较常规灌排模式节水16.7%,增产7.1%,排水总量减少54%,水稻全生育期稻田排水中NH4+;-N、NO3-N与TP流失总量分别减少38.07%、82.29%和52.15%,节水减排和降污效果显著.采用控制灌排模式,通过实施灌水调控和排水管理.控制了氮磷流失关键时期的排水量.高效利用了水分和养分,取得了节水高产、减排控污的效果.     

Prediction of daily reference evapotranspiration by a multiple regression method based on weather forecast data

Prediction of daily reference evapotranspiration (ET ₀) is the basis of real-time irrigation scheduling. A multiple regression method for ET ₀ prediction based on its seasonal variation pattern and public weather forecast data was presented for application in East China. The forecasted maximum temperature (T _max), minimum temperature (T _min) and weather condition index (WCI) were adopted to calculate the correction coefficient by multilinear regression under five time-division regimes (10 days, monthly, seasonal, semi-annual and annual). The multiple regression method was tested for its feasibility for ET ₀ prediction using forecasted weather data as the input, and the monthly regime was selected as the most suitable. Average absolute error (AAE) and root mean square error (RMSE) were 0.395 and 0.522 mm d^?1, respectively. ET ₀ prediction errors increased linearly with the increase in temperature prediction error. A temperature error within 3 K is likely to result in acceptable ET ₀ predictions, with AAE and average absolute relative error (AARE) <0.142 mm d^?1 and 5.8%, respectively. However, one rank error in WCI results in a much larger error in ET ₀ prediction due to the high sensitivity of the correction coefficient to WCI and the large relative error in WCI caused by one rank deviation. Improving the accuracy of weather forecasts, especially for WCI prediction, is helpful in obtaining better estimations of ET ₀ based on public weather data.     

西北牧区灌溉人工草地适宜发展规模分析

针对西北牧区水资源和草地资源已被超极限利用的现状,应用水草畜平衡原理,分析了西北牧区灌溉人工草地的发展规模,提出了西北牧区灌溉人工草地适宜发展规模为215.76～239.71万hm^2,载畜量控制在13833.18万羊单位之内即可实现草畜平衡,总体可达到人工种植冷季补饲水平。新增灌溉需水量约为71.85～83.55亿m^3,占2000年灌溉总用水量（777亿m^3）的9.25%～10.75%。解决这一灌溉需水量的可行途径是建设节水型社会,提高水资源利用效率。     

基于有限体积法的含无压段泵站水锤模拟及调压井优化

针对含无压段的泵站输水工程水锤模拟常采用特征线法，且往往忽略动态摩阻和有压-无压相互干扰影响的问题，该研究建立了考虑动态摩阻的二阶有限体积法模型，进行有压段-无压段实时联合计算。首先，采用二阶Godunov格式分别对有压流、无压流流动控制方程进行求解，同时考虑了动态摩阻效应以准确模拟水力瞬变过程中的能量耗散，并进行试验验证。进一步地，对有压段、无压段交接处采用变时步法传递数据，结合实际工程对阻抗式调压井的尺寸、位置进行了敏感性分析。结果表明：考虑动态摩阻效应后模型模拟结果与试验结果基本一致，阀门处水锤压力误差最大值仅有4.58%；与特征线法相比，二阶Godunov格式稳定性更高，库朗数小于1时水锤压力只有轻微的数值衰减。本文建立的有压段-无压段实时联合计算方法能够充分考虑有压段出水池水位变化以及无压段倒流的影响。针对水泵失电工况，对阻抗式调压井进行的优化研究表明，随连接管直径增大，系统内最大压力水头、调压井最高涌浪水位和水泵最大反转转速增大，调压井最低涌浪水位降低；随调压井直径增大，最高涌浪减小，最低涌浪增高，最大压力在连接管直径较小时一直降低，在连接管直径较大时先减小后增大；当连接管管径 3.5 m，调压井直径 15 m 时， 既能满足系统控制参数要求，也能减少工程量。调压井位置离泵站越近，最大压力、反转转速、最高涌浪越大，最低涌浪越小，当调压井布置在泵后1.0 km时，最高涌浪水位会达到172.35 m，不满足控制标准要求。综上，建立的模型具有较高的准确性、稳定性和适用性，研究结果可为含无压段泵站输水工程的水锤模拟提供参考。     

Yield and water consumption characteristics of wheat/maize intercropping with reduced tillage in an Oasis region

Higher irrigation quota for conventional farming causes substantial conflicts between water supply and demand in agriculture, and wind erosion near soil surface is one of the major causes of farmland degradation and desertification in arid areas. This research investigated the effect of the amounts of irrigation in combination with tillage practices on soil evaporation (E), water consumption (ET) characteristics, and grain yield performance and water use efficiency (WUE) for wheat (Triticum aestivum L.) intercropped with maize (Zea mays L.) in strip planting in an Oasis region. The field experiment, conducted at Wuwei station during 2008–2010, had two tillage systems (reduced tillage with wheat stubble retention vs. conventional tillage without stubble retention), and three (low, medium, and high) levels of irrigation, in a randomized complete block design. Averaged across three years, soil evaporation with medium and high levels of irrigation was 6.8% and 5.4% greater than that with low level of irrigation, respectively. Total water consumption of wheat/maize crops under the medium and high irrigation levels was 8.5% and 18.5% greater, respectively, than that under low irrigation. However, grain yields were similar under the medium and high levels of irrigation, so was WUE. The effect of tillage on the wheat/maize intercropping was inconsistent across years or among treatments: soil moisture at harvest was 3.0–7.6% greater in the fields with reduced tillage compared with those with conventional tillage in 2008 and 2009, but no difference was found in 2010; the E/ET ratio of reduced tillage was 9% lower than the ratio under conventional tillage in 2008, 3% higher in 2010, but no difference between the two tillage systems in 2009. Across three years, there was a general trend that the WUE of the wheat/maize intercropping system with reduced tillage was greater (by 4–11%) than that with conventional tillage. We conclude that a medium level of irrigation is sufficient to achieve crop yields and WUE equivalent to those under high level of irrigation, provided that a reduced tillage practice is applied to the wheat/maize intercropping in Oasis areas.     

Cover crops alter the soil nematode food web in banana agroecosystems

Cover crops are increasingly being used in agriculture, primarily for weed or erosion management. The addition of cover crops increases the primary productivity of the system and diversifies basal resources for higher trophic levels. How increases in the quality and quantity of basal resources affect bottom-up and top-down control remains a key question in soil food web ecology. We evaluated the response of the nematode community to the introduction of cover crops between rows of a banana plantation. We measured changes in nematode food web structure and inferred the prevalence of bottom-up and top-down effects on the abundance of phytophagous nematodes (i.e., plant-feeding and root-hair-feeding species) 1.5 years after plots with cover crops (Poaceae or Fabaceae species) or bare soil were established. The addition of a cover crop greatly affected the structure and the abundance of the soil nematode community 1.5 years after planting. The abundance of all trophic groups except for plant-feeding nematodes tended to increase with the addition of cover crops. The Shannon–Weaver diversity index and the enrichment index increased with the addition of cover crops, indicating that opportunistic, bacterivorous and fungivorous nematodes benefited from the added resources. Plant-feeding nematodes were least abundant in plots with Poaceae cover crops, while bacterivorous, omnivorous, and root-hair-feeding nematodes were more abundant with Fabaceae cover crops than with bare soil, indicating that cover crop identity or quality greatly affected soil food web structure. Bottom-up effects on all trophic groups other than plant-feeding nematodes were evident with Poaceae cover crops, suggesting an top-down control of plant-feeding nematodes by omnivorous nematodes. Conversely, plant-feeding nematodes were evidently not suppressed in Fabaceae cover crops, perhaps because bottom-up effects on omnivorous nematodes were weaker (hence, top-down control by omnivorous nematodes was weaker), and because Fabaceae cover crops probably served as good hosts for some plant-feeding nematodes.     

Subsurface drainage performance study using SALTMOD and ANN models

Relative performance of artificial neural networks (ANNs) and the conceptual model SALTMOD was studied in simulating subsurface drainage effluent and root zone soil salinity in the coastal rice fields of Andhra Pradesh, India. Three ANN models viz. Back Propagation Neural Network (BPNN), General Regression Neural Network (GRNN) and Radial Basis Function Neural Network (RBFNN) were developed for this purpose. Both the ANNs and the SALTMOD were calibrated and validated using the field data of 1998–2001 for 35 and 55 m drain spacing areas. Data on irrigation depth, evapotranspiration, drain discharges, water table depths, mean monthly rainfall and temperature and drainage effluent salinity were used for ANN model training, testing and validation. It was observed that the BPNN model with feed forward learning rule with 6 processing elements in input layer and 1 hidden layer with 12 processing elements performed better than the other ANN models in predicting the root zone soil salinity and drainage effluent salinity. Considering coefficient of determination, model efficiency and variation between the observed and predicted salinity values as the evaluation parameters, the SALTMOD performed better in predicting root zone soil salinity and the BPNN performed better in predicting the drainage effluent salinity. Therefore, it was concluded that the BPNN with feed forward learning algorithm was a better model than SALTMOD in predicting salinity of drainage effluent from salt affected subsurface drained rice fields.     

抽蓄机组甩负荷过程压力脉动及流动噪声仿真

为了研究水泵水轮机发电模式下甩负荷过渡过程压力脉动特性及其对流动诱导噪声的影响,以国内某抽水蓄能电站机组为研究对象,基于网格壁面滑移技术与分离涡湍流模型,通过ANSYS软件对瞬态流场进行数值模拟计算,并将所得流场信号作为声场源在LMS软件中进一步开展流动诱导噪声的仿真.结果表明因2个无叶区流态分别受动静干涉(固定导叶与活动导叶间)与动动干涉(活动导叶与转轮间)影响,导叶两侧压力变化趋势完全不同.转轮流道内压力脉动主频位置在叶频St为0.676 3处,水泵水轮机内声场噪声分布呈现明显的偶极子特性,小流量(0.2Q_BEP以下)时内场声压变化相对剧烈,最大声压值高达130.00 dB,最小声压为9.67 dB.不同时刻外声场声压级表现出极为相似的波动性,整体趋势表现为声源强度随流量减小而增加,但是流量变化对噪声指向性分布型式并无影响,说明对水泵水轮机内部压力脉动情况改善有助于降低流动诱导噪声水平.