基于随机降雨模拟的灌区塘坝蓄水方案优化

结合南方丘陵灌区塘坝分布广、数量多、群体容量大的特点,建立库塘水资源系统优化调控模型。以漳河灌区的子灌区——杨树垱水库灌区为研究实例,应用蒙特卡洛法模拟出长序列的旬降雨,采用正交试验法选出每个模拟年份的最优塘坝控制运行方案,并对控制运行规律进行统计分析,得到不同典型年下塘坝的控制运行规则：在平水年时5月底、6月上旬末、6月下旬末、7月上旬末预留30%,6月中旬末预留10%,7月中旬末预留20%,其他各旬可全部用完;在偏枯水年时5月底预留10%,6月上旬末、6月下旬末预留20%,6月中旬末、7月上旬末、7月中旬末预留30%,其他各旬可全部用完;在特枯水年时5月底、7月中旬末预留10%,6月上旬末、6月中旬末预留30%,6月下旬末、7月上旬末、7月下旬末预留20%,其他各旬可全部用完。比较塘坝在不控制运行与优化控制运行下保证基本产量的概率,结果表明：在平水年时,相对产量在0.6以上的概率提高了2.38%;在偏枯水年时,相对产量在0.6以上的概率提高了8.80%;在特枯水年时,相对产量在0.6以上的概率提高了11.29%。研究从定量分析的角度,以单位面积产量最大为目标,提出塘坝的控制运行规则,对指导水库、塘坝的联合运行,提高灌区的灌溉效益具有重要意义。     

灌渠闭闸期闸前段流场特征及泥沙淤积速率分析

为研究灌渠闭闸期闸前段流场特征及泥沙淤积速率,基于南亚某河流待建引水明渠建立水流数学模型,并借助Flow-3D软件对高水位、中水位和低水位3种特征工况下,闭闸期闸前段流场进行模拟分析。依据盲肠水流泥沙运动的研究思路,提出闭闸期闸前明渠段泥沙淤积速率的估算方法,并结合同期明渠段悬移质泥沙模型试验资料,率定得出闸前段泥沙淤积速率求解公式。结果表明,闭闸期闸前段出现围绕竖轴近似呈椭圆型的回流现象,平面流速呈交替增减、水位呈中心低周界高的水力特征;泥沙淤积速率较大,灌渠将呈现累积性淤积特征。最终得出,闭闸期闸前明渠段与港池内盲肠水流运动相类似,闸前渠段淤积严重,引水明渠的口门初步设计方案有待充分论证的结论。     

考虑基土不均匀冻胀的梯形渠道混凝土衬砌弹性地基梁力学模型

为了探究寒区高地下水位引起渠道基土不均匀冻胀对梯形渠道混凝土衬砌冻胀的影响作用，该研究在前期提出的弹性地基梁模型基础上，将基土不均匀冻胀对边坡衬砌板的作用等效为作用在衬砌板上的荷载，给出在边坡衬砌板在基土发生不均匀冻胀的情况下其冻胀量，冻胀反力，弯矩和剪力的计算方法。以甘肃省高液限土壤，地下水位5 m地区的边坡系数为1的渠道为例，探究不同边坡衬砌板长度和不均匀冻胀基土之间的相互作用。结果表明，边坡衬砌板长度每增加1 m，冻胀反力最大值增大142%，弯矩最大值平均增大223%。同时，弯矩最大值点会从原来的距坡脚1/3左右处向坡脚偏移。因此，在寒区的高水位地区进行渠道设计的过程中，建议尽可能设计为宽浅式横断面，以减少由地下水引起的基土不均匀冻胀对渠道衬砌板的影响。同时，以边坡衬砌板长度为4 m为例，探究了基土均匀冻胀和不均匀冻胀对边坡衬砌板影响的差异，得出基土不均匀冻胀的冻胀反力最大值和弯矩最大值，分别比基土均匀冻胀大264%和170%。因此，在寒区高水位地区进行渠道抗冻胀衬砌设计时，宜按基土非均匀冻胀弹性地基梁模型计算。     

冰盖下梯形及抛物线形输水明渠正常水深显式迭代算法

随着冬季用水量的增加,越来越多的输水工程在冬季冰盖下输水,冰盖下输水已经成为一种常态化输水方式,但目前对明渠正常水深的显式计算方法的研究主要针对不结冰渠道的,缺少对冰盖下输水时正常水深的显式计算方面的研究。该文推导了梯形断面冰盖下输水时正常水深和流量关系,提出了正常水深的简易显式迭代算法,并经过证明,此迭代算法是收敛的。用同样的方法,推导了抛物线形断面冰盖下输水时正常水深和流量关系,提出了计算正常水深的简易显式迭代算法。算例表明,该文提出的冰盖下梯形断面和抛物线形断面的显式迭代算法具有形式简单、计算量小、精度高,收敛性好的特点,一般需要3~5次迭代就可使误差小于0.01 m,当增大迭代次数时,误差进一步减小。研究为冰盖下输水渠道正常水深计算提供了便捷的计算方法,对冰期输水渠道的设计及运行管理具有理论和实践意义。     

基于多源信息融合决策的灌区生态环境评价指标优选

针对目前灌区生态环境评价研究中指标选取主观化、未成体系化的困境,该研究提出了一种基于指标多源特征信息融合的优选思路与方法。以关中地区泾惠渠灌区为研究对象,通过构建灌区生态环境概念模型,以"灌区资源"定义因素层,逐级确定了31个指标,初步构建了灌区生态环境评价指标库。采集指标灵敏度、均衡度、独立性这3种特征信息,视为3项证据,进而采用DS(Dempster Shafer)证据理论对该3项证据基本信任分配函数值进行融合,计算该3项证据共同支持作用下的指标可信度,依据可信度高低排序结果,即可从繁复、庞大的指标库中进行指标优选。该研究设置了两种融合思路:1指标全体融合、2先分别剔除3项证据下基本信任分配函数值较低的指标,然后对剩余指标进行融合;并进行对比分析研究,结果表明:第2种思路下的计算会提前剔除某些可信度较高的指标,如盐碱化程度、空气相对湿度指标;按照第1种思路,对指标全体进行信息融合,进而根据可信度排序结果,选取可信度较高的指标作为灌区生态环境评价研究的主评指标,为灌区生态环境健康评价提供了支撑。为其他领域评价研究中指标的优选提供了新的思路和决策方法。     

基于自由搜索算法的灌渠配水优化模型

国内外现有的渠道配水模型是建立在下级渠道流量相等、上级渠道断面均匀水力参数相同的基础上,无疑限制了模型的应用范围。针对该种不足,该文建立了考虑下级渠道流量不等和上级渠道断面变化的精细化配水模型。在模型求解方面,通过构建合理的适应度函数和对约束条件的高效处理,应用自由搜索算法对模型进行了求解。应用结果表明,采用本模型和算法得到的配水方案与原配水方案相比,输水渗漏损失减少了8.26%;配水过程也更加均匀,有效减少了闸门调节次数。     

大型灌区节水水平评价指标体系构建与实证

灌区是中国农业节水的主战场,对灌区节水水平进行评价可为灌区现代化改造提供借鉴与指导,合理适用的评价指标体系是进行灌区节水水平评价的核心内容。针对当前灌区评价指标选取存在的冗余、不完备的问题,为构建满足简洁性与完备性的反映灌区节水水平的评价指标体系,该研究从工程节水、田间节水、用水管理、水资源保护及用水效益5个方面初步建立了大型灌区节水水平评价指标体系,利用筛选模型从70个指标中优选出了23个灌区节水评价指标,表达了86.42%的信息,使最终的指标体系兼具简洁性与完备性,并对河南省沿黄渠村灌区、彭楼灌区、广利灌区、大功灌区4处大型灌区进行了节水水平实证研究。结果表明,4处灌区相应的节水评价指数分别为0.666、0.730、0.657、0.616,其中彭楼灌区由于具有较高的骨干渠系配套程度和明显的工程节水优势使其整体节水水平较高,渠村灌区和广利灌区的节水水平次之,大功灌区的节水水平相对较低;受益于大型灌区续建配套与节水改造项目4处灌区在工程节水方面表现相对较好,评价结果与实际情况相符,表明该研究构建的节水水平评价指标体系科学合理;为进一步提升灌区的节水水平,4处灌区需加强用水管理水平、增加用水效益以及注重水资源保护建设。研究成果为科学评估大型灌区节水建设提供了一种有效的方法,并对推进农业节水化进程具有积极的指导作用。     

Two-way coupling of unsaturated-saturated flow by integrating the SWAT and MODFLOW models with application in an irrigation district in arid region of West China

This paper presents the realization of two-way coupling of the unsaturated-saturated flow interactions of the SWAT2000 and MODFLOW96 models on the basis of the integrated surface/groundwater model SWATMOD99, and its application in Hetao Irrigation District (HID), Inner Mongolia, China. Major revisions and enhancements were made to the SWAT2000 and MODFLOW models for simulating the detailed hydrologic budget and coupled unsaturated and saturated interactions, and irrigation canal hydrology for the HID. The simulation results of seasonal groundwater recharge to and evaporate from the shallow groundwater, and the annual water budget over the district are presented and discussed. The results implied the necessity of two-way coupling of the unsaturated-saturated interactions when groundwater is shallow, and the feasibility of making comprehensive use of the information coming from both the surface water and groundwater models to make a more physically-based assessment of the coupled interactions.     

Review of the use of transrectal ultrasonography for evaluation of the caudal lumbar – including lumbosacral – intervertebral discs and symphyses: Normal and abnormal ultrasonographic appearance

Transrectal ultrasonography of the lumbosacroiliac area is routinely performed for the diagnosis of the cause of low back pain and poor hindlimb impulsion and engagement. The ventral aspect of the caudal lumbar intervertebral discs and vertebrae can be easily assessed transrectally with ultrasound while other imaging modalities have limitations for diagnosis of intervertebral disc injuries. This paper is a review of the ultrasonographic procedure for imaging the ventral aspect of the caudal lumbar and lumbosacral symphyses, especially the intervertebral discs. Normal images, findings and lesions of the three caudalmost lumbar intervertebral discs are described (between the 4th lumbar and the 1st sacral vertebrae).     

MR-imaging of lumbosacral intervertebral disc degeneration in clinically sound German shepherd dogs compared to other breeds

German shepherd dogs are overrepresented in the group of dogs with cauda equina compression syndrome due to degenerative lumbosacral stenosis. A congenital predisposition for early degeneration of the lumbosacral intervertebral disc has been suspected. Our aims were to assess the morphologic appearance of the lumbosacral intervertebral disc and the lumbosacral junction in healthy German shepherd dogs compared to other breeds and to evaluate for an early onset of degenerative changes. The lumbosacral spine of 110 clinically sound German shepherd dogs and 47 healthy dogs of other large breeds was examined using magnetic resonance (MR) imaging. The degeneration of every intervertebral disc was graded using an established classification system. Signal intensity of the entire lumbosacral disc and the nucleus pulposus was determined independently. Lumbosacral malalignment was assessed according to a previously described method. The findings for the German shepherd dogs were compared to those of the other breeds. Although most dogs were younger than 18 months at the date of examination, significantly higher grades of degeneration were detected for the lumbosacral intervertebral disc of German shepherd dogs (P < 0.003). Degeneration of the lumbosacral intervertebral disc was independent from findings in the other lumbar discs. We conclude that the German shepherd dog has a predisposition for degenerative changes in the lumbosacral intervertebral disc.