Simulated impacts of irrigation on evapotranspiration in a strongly exploited region: a case study of the Haihe River basin,China

Irrigation is the major water supply for crop production in water‐limited regions. However, this important water component is usually neglected or simplified in hydrological modelling primarily because information concerning irrigation is notably difficult to collect. To assess real effects of irrigation on the simulation of evapotranspiration (ET) in water‐limited region, the Community Land Model version 4 was established over a typical semi‐humid agricultural basin in the northern China – the Haihe River basin. In the irrigated cropland, incorporating an irrigation scheme can enhance the simulated ET and improve the simulation of spatial variability of soil moisture content. We found that different configurations in the irrigation scheme do not cause significant differences in the simulated annual ET. However, simulated ET with simulated irrigation differs clearly from that with observed irrigation in mean annual magnitude, long‐term trend and spatial distribution. Once the irrigation scheme is well‐calibrated against observations, it reasonably reproduces the interannual variability of annual irrigation, when irrigation water management is relatively stable. More importantly, parameter calibration should be consistent with the configuration of the source of irrigation water. However, an irrigation scheme with a constant parameter value cannot capture the trend in the annual irrigation amount caused by abrupt changes in agricultural water management. Compared with different remotely sensed ET products, the enhancement in the simulated ET by irrigation is smaller than the differences among these products, and the trend in simulated ET with the observed irrigation cannot be captured correctly by the remotely sensed ET. Copyright © 2014 John Wiley & Sons, Ltd.     

Fracability Evaluation Based on the Three-Dimensional Geological Numerical Simulation of In Situ Stress: Case Study of the Longmaxi Formation in the Weirong Shale Gas Field,Southwestern China

Mathematical Geosciences - Quantitative evaluation of fracability is essential for hydraulic fracturing design, with the distribution of in situ stress being a key parameter. This study focused on...     

潮白河流域降水演变及其径流效应

分析了潮白河流域1991~2000年降水资料时空演变规律,采用同倍比放大法对各年的降水数据进行整体轮换处理,处理后各年总降水量为1991~2000年的平均年降水量。随后基于GBHM(Geomorphology-Based Hydrological Model)模型进行了10年径流量模拟。结果显示,在降水总量相同的情况下,1994年型降水时空分布最有利于产流,径流总量与峰值流量最大,1999年型径流总量与峰值流量最小。1994年型径流总量是1999年型径流总量的3.88倍;1994年型峰值流量是1999年型峰值流量的35.87倍。由此可见,降水总量相同时,其时空分布对径流总量和峰值的影响极大。     

电镀废水改进的CAFE处理工艺设计及案例

电镀园区废水处理过程中,由于园区企业难以做到彻底的分质分流,导致废水处理出现破络不彻底,次亚磷酸盐、氰化物等出现再络合与难降解等问题,同时,深度处理后,浓水需要进行深度处理,重金属离子浓度、总磷、总氮处理都存在难以达标的情况。本文根据企业电镀废水的典型水质和水量特征,研究设计了改进的CAFE处理工艺,详细论证了各工艺的处理过程、主要设备及相关设计参数,并将该工艺在南通某电镀园区电镀废水处理中进行了实际应用。运行的实践表明,该套设计方案污水处理运行稳定,最终出水的COD_Cr（化学需氧量）、NH₄-N、总铬、六价铬、总镍指标的平均质量浓度分别为34.00、5.41、0.29、0.03、0.05 mg/L,均远远小于电镀废水的排放标准,达到了电镀废水的深度处理要求。     

北麓河多年冻土区降水及河水稳定同位素特征分析

为了进一步全面理解和探索青藏高原水文水循环过程,采用同位素方法并结合气象资料对青藏高原北麓河区域2011年6~12月降水和河水稳定同位素时空特征进行分析。探讨了北麓河降水同位素与日平均气温、降水量之间的相互关系,同时也对比分析了北麓河降水和河水的同位素变化特征。结果表明:北麓河降水同位素在整个观测期内总体受温度控制,但存在季节变化,其中6~9月降水同位素受到温度和降水量效应的共同控制,9月以后则主要受温度的影响。河水同位素与降水同位素相似的变化特征,体现了降水补给特征,另外降水量也能够影响河水同位素变化:降水量小则降水对其影响较小,反之则大。与北麓河降水线相比,河水δ18O~δD关系的斜率和截距偏大,揭示该区域河水除了受大气降水的补给外,还受到区域水体内循环和蒸发分馏作用的影响。     

基于GIS的处理服务构建方法

伴随着GIS技术的逐步发展和日渐成熟,人们对地理信息提出了更高的要求,促进了地理信息系统向地理信息服务方向发展。地理信息服务主要包括数据服务和处理服务两部分,目前,大多数厂商提供的地理信息服务仅局限于数据服务层面,处理服务较少实现。本文通过对处理服务原理及构建方法的研究,基于国家基础地理信息中心的全球地表覆盖动态信息系统,在Visual Studio 2010平台下实现了将功能封装为处理服务,并在服务流程编排的基础上实现处理服务的调用。     

Understanding hydrological trends by combining the Budyko hypothesis and a stochastic soil moisture model

Abstract

The actual evapotranspiration and runoff trends of five major basins in China from 1956 to 2000 are investigated by combining the Budyko hypothesis and a stochastic soil moisture model. Based on the equations of Choudhury and Porporato, the actual evapotranspiration trends and the runoff trends are attributed to changes in precipitation, potential evapotranspiration, rainfall depth and water storage capacity which depends on the soil water holding capacity and the root depth. It was found that the rainfall depth increased significantly in China during the past 50 years, especially in southern basins. Contributions from changes in the water storage capacity were significant in basins where land surface characteristics have changed substantially due to human activities. It was also observed that the actual evapotranspiration trends are more sensitive to precipitation trends in water-limited basins, but more sensitive to potential evapotranspiration trends in energy-limited basins.

Editor D. Koutsoyiannis; Associate editor A. Porporato     

不同滤波系数在电磁法数值计算中的应用研究

电磁法存在大量的汉克尔积分,由于积分核函数的复杂性,该类积分不存在解析解,采用数值方法求解汉克尔积分是电磁法正演研究中的关键问题。数值滤波法运算速度快、执行效率高,克服了被积函数的奇异性和高振荡性问题,是数值求解汉克尔积分的重要方法。采用存在解析解的汉克尔积分,对比研究了5套高精度汉克尔滤波系数,总结了不同数值滤波算法的计算精度和误差分布特点。结果表明,5套数字滤波的快速汉克尔变换算法在逼近相应的理论解析解时,不存在振荡现象,且计算精度高;汉克尔积分计算精度均随着发收距的增大而降低;计算精度并不一定随着数值滤波系数个数的增多而提高。分别采用5种滤波系数对水平电偶极子和垂直磁偶极子的电磁场进行计算,得到的电场和磁场的形态基本一致。     

基于遥感图像地形结构-岩性组分分解的岩类多重分形特征研究

根据光学成像原理和地形结构的分形特征,提出了遥感图像的地形结构-岩性组分模型和分离算法,并用于ETM图像分解和岩类α-f(α)多重分形特征研究。通过对不同地区二长花岗岩体和沉积变质岩ETM原图像、地形结构子图像和岩性组分子图像的多重分形谱对比分析,发现原始ETM图像的多重分形谱与岩石类型和地形没有明显的对应关系。图像分解后,不同地区的二长花岗岩具有十分相似的岩性组分多重分形谱和不同的地形结构多重分形谱;相反,同一地区的不同类型岩石具有相似的地形结构多重分形谱和不同的岩性组分多重分形谱。因此,利用地形结构-岩性组分分类算法,并结合α-f(α)多重分形谱分形,可以有效地区分岩石类型。