基于分布式大流域径流模型的中国西北黑河流域水文模拟

水资源短缺是中国西北干旱地区长期的问题,区域人口增加、城市化扩张,加之气候变化的影响进一步加剧了西北地区水资源短缺,也使生活用水、灌溉用水、工业用水和维持生态系统稳定的用水危险加剧.采用分布式大流域径流模型(DLBRM)模拟黑河流域水文(中国第二大内陆河,流域面积128 000 km2)来理解区域的冰川和积雪融化水、地下水、地表水、蒸散发等方面的分布,评估气候变化对水文的影响和冰川退缩对中游和下游来水量的影响.模拟结果表明,黑河流域的大部分产流那源于黑河上游地区的祁连山.模拟1990-2000年黑河河流日流量变化结果认为,黑河中游正义峡给下游的供水为10×108m3,其中地表径流占51%,层间流占49%.中游地区沙土具有较高的蒸腾发能力,近一半的地表水被蒸发掉.模拟实践证明,分布式大流域径流模型可以结合气候变化、水资源管理方面的成果,改进流域水文模拟的精度.     

“蒸发悖论”在黑河流域的探讨

利用黑河流域12个气象站点1960-2010年的气象资料,运用FAO Penman-Monteith模型计算潜在蒸散量,采用旋转经验正交函数、Mann-Kendall检验等方法系统分析了过去51 a间潜在蒸散量及气温的变化趋势,重点对"蒸发悖论"在黑河流域的规律进行分析.结果表明:根据潜在蒸散量的旋转经验正交函数分区结果,黑河流域可以划分为4个子区."蒸发悖论"仅于1960-1993年存在于黑河流域河西走廊区(Ⅱ区、Ⅲ区);其它各区无"蒸发悖论".1994-2010年由于潜在蒸散量的显著上升,河西走廊区"蒸发悖论"消失.1993年是黑河流域潜在蒸散量变化趋势的一个转折点,1994-2010年黑河流域的潜在蒸散量表现为统计显著的上升趋势.风速的变化是影响黑河流域河西走廊区"蒸发悖论"出现和消失的重要因素.     

流域科学与水资源管理

流域是水资源管理的基本单位。基于水资源文献的综合分析,讨论了自20世纪以来水资源管理概念、目标及途径的变迁,提出建立流域科学,以流域为研究对象,以揭示流域生态水文过程的客观规律为前提,采用现代管理科学理论和方法,应用先进工程技术手段优化配置水资源,满足人类活动及生态系统的多种需求,促进社会、经济及环境的可持续发展。并且指出流域科学的内涵应包括:①水资源的调查、监测和模拟;②水资源利用多目标设定;③水资源分配机制;④水资源管理指标的确定与评价;⑤水资源管理决策机构;⑥水资源管理反馈分析与人类活动调控。     

Modelling the impacts of spatial heterogeneity in soil hydraulic properties on hydrological process in the upper reach of the Heihe River in the Qilian Mountains,Northwest China

Spatial heterogeneity of soil has great impacts on dynamic processes of the hydrological systems. However, it is challenging and expensive to obtain spatial distribution of soil hydraulic properties, which often requires extensive soil sampling and observations and intensive laboratory analyses, especially in high elevation, hard to access mountainous areas. This study evaluates the impacts of soil heterogeneity on hydrological process in a high elevation, topographically complex watershed in Northwest China. Two approaches were used to derive the spatial heterogeneity of soil properties in the study watershed: (1) the spatial clustering method, Full‐Order‐CLK was used to determine five soil heterogeneous clusters (configurations 97, 80, 60, 40 and 20) through large number of soil sampling and in situ observations, and (2) the average values of soil hydraulic properties for each soil type were derived from the coarse provincial soil data sets (Gansu Soil Handbook at 1 : 1 000 000 scale). Subsequently, Soil and Water Assessment Tool model was used to quantify the impact of the spatial heterogeneity of soil hydraulic properties on hydrological process in the study watershed. Results show the simulations by Soil and Water Assessment Tool with the spatially clustered soil hydraulic information from the field sampling data had much better representation of the soil heterogeneity and had more accurate performance than the model using the average soil property values for each soil type derived from the coarse soil data sets. Thus, incorporating detailed field sampling, soil heterogeneity data greatly improve performance in hydrological modelling. Copyright © 2015 John Wiley & Sons, Ltd.     

Applicability of cosmic-ray neutron sensor for measuring soil moisture at the agricultural-pastoral ecotone in northwest China

Accurate monitoring of soil moisture is crucial in hydrological and ecological studies. Cosmic-ray neutron sensors (CRNS) measure area-average soil moisture at field scale, filling a spatial scale gap between in-situ observations and remote sensing measurements. However, its applicability has not been assessed in the agricultural-pastoral ecotone, a data scarce semi-arid and arid region in Northwest China (APENC). In this study, we calibrated and assessed the CRNS (the standard N₀ method) estimates of soil moisture. Results show that Pearson correlation coefficient, R_P, and the root mean square error (RMSE) between the CRNS soil moisture and the gravimetric soil moisture are 0.904 and less than 0.016 m³ m⁻³, respectively, indicating that the CRNS is able to estimate the area-average soil moisture well at our study site. Compared with the in-situ sensor network measurements (ECH2O sensors), the CRNS is more sensitive to the changes in moisture in its footprint, which overestimates and underestimates the soil moisture under precipitation and dry conditions, respectively. The three shape parameters a₀, a₁, a₂ in the standard calibration equation (N₀ method) are not well suited to the study area. The calibrated parameters improved the accuracy of the CRNS soil moisture estimates. Due to the lack of low gravimetric soil moisture data, performance of the calibrated N₀ function is still poor in the extremely dry conditions. Moreover, aboveground biomass including vegetation biomass, canopy interception and widely developed biological soil crusts adds to the uncertainty of the CRNS soil moisture estimates. Such biomass impacts need to be taken into consideration to further improve the accuracy of soil moisture estimation by the CRNS in the data scarce areas such as agricultural-pastoral ecotone in Northwest China.

     

Development of an Instant Correction and Display System of Numerical Weather Prediction Products in China

This paper presents the development of numerical prediction products （NPP） correction and display system （NPPCDS） for rapid and effective post-processing and displaying of the T213 NPP （numerical prediction products of the medium range numerical weather prediction spectral model T213L31） through instant correction method. The NPPCDS consists of two modules： an automatic correction module and a graphical display module. The automatic correction module automatically corrects the T213 NPP at regularly scheduled time intervals, while the graphical display module interacts with users to display the T213 NPP and its correction results. The system helps forecasters extract the most relevant information at a quick glance without extensive post-processing. It is simple, easy to use, and computationally efficient, and has been running stably at Huludao Meteorological Bureau in Liaoning Province of China for the past three years. Because of its low computational costs, it is particularly useful for meteorological departments that lack advanced computing capacity and still need to make short-range weather forecasting.     

土壤水文属性及其对水文过程影响研究的进展、挑战与机遇

土壤水文属性对水文过程、能量过程、碳氮循环过程及各过程间相互作用有重要影响.首先简要回顾近30年来土壤水文属性的研究进展,包括土壤水文属性的监测分析、土壤水文属性对水文过程的影响机理,以及不同尺度土壤水文属性对水文过程的影响差异及联系.其次,论述土壤水文属性研究的挑战与机遇.最后介绍祁连山区土壤水文属性对水文过程的影响及多尺度特征研究.力求加深对土壤水文属性变异规律及其对水文过程影响机理的认知,发展土壤水文学和山区水文学,支持水资源科学管理和区域可持续发展.     

A Modified Groundwater Module in SWAT for Improved Streamflow Simulation in a Large,Arid Endorheic River Watershed in Northwest China

Interactions between surface water and groundwater are dynamic and complex in large endorheic river watersheds in Northwest China due to the influence of both irrigation practices and the local terrain. These interactions interchange numerous times throughout the middle reaches, making streamflow simulation a challenge in endorheic river watersheds. In this study, we modified the linear-reservoir groundwater module in SWAT (Soil and Water Assessment Tools, a widely used hydrological model) with a new nonlinear relationship to better represent groundwater processes; we then applied the original SWAT and modified SWAT to the Heihe River Watershed, the second largest endorheic river watershed in Northwest China, to simulate streamflow. After calibrating both the original SWAT model and the modified SWAT model, we analyzed model performance during two periods: an irrigation period and a non-irrigation period. Our results show that the modified SWAT model with the nonlinear groundwater module performed significantly better during both the irrigation and non-irrigation periods. Moreover, after comparing different runoff components simulated by the two models, the results show that, after the implementation of the new nonlinear groundwater module in SWAT, proportions of runoff components changed-and the groundwater flow had significantly increased, dominating the discharge season. Therefore, SWAT coupled with the non-linear groundwater module represents the complex hydrological process in the study area more realistically. Moreover, the results for various runoff components simulated by the modified SWAT models can be used to describe the hydrological characteristics of lowland areas. This indicates that the modified SWAT model is applicable to simulate complex hydrological process of arid endorheic rivers.     

CLM4.5在西北农牧交错带盐池站的模拟性能评估

农牧交错带具有草地、裸地、农田大面积相互镶嵌的独特下垫面,其地表水热过程变化复杂,亟需深入研究。利用宁夏盐池站2017年实际观测资料,对陆面过程模式CLM4.5的模拟性能进行检验。结果表明,在复杂下垫面下,CLM4.5仍能较好地模拟出草地的地面反射辐射、地面长波辐射和净辐射以及0~10 cm土壤含水量和温度的变化特征,但模拟值与观测值还存在一定偏差。CLM4.5能模拟出辐射通量的日变化特征,除5月外,地面反射辐射模拟值与观测值之间的偏差较小。地面长波辐射模拟值白天偏高,净辐射观测值与模拟值的相关系数为0.99,均方根误差为22.50 W·m^-2。土壤含水量观测值与模拟值的相关系数达0.83,但模拟值偏低,且模式对降雨后土壤含水量变化过程的模拟性能有待提高。土壤温度模拟值的日变化特征较为明显,观测值与模拟值的相关系数为0.98,均方根误差为2.82℃。     

Evaluation of the SMOS and SMAP soil moisture products under different vegetation types against two sparse in situ networks over arid mountainous watersheds,Northwest China

Assessment of the suitability of satellite soil moisture products at large scales is urgently needed for numerous climatic and hydrological researches, particularly in arid mountainous watersheds where soil moisture plays a key role in landatmosphere exchanges. This study presents evaluation of the SMOS(L2) and SMAP(L2_P_E and L2_P) products against ground-based observations from the Upstream of the Heihe River Watershed in situ Soil Moisture Network(UHRWSMN) and the Ecological and Hydrological Wireless Sensor Network(EHWSN) over arid high mountainous watersheds, Northwest China.Results show that all the three products are reliable in catching the temporal trend of the in situ observations at both point and watershed scales in the study area. Due to the uncertainty in brightness temperature and the underestimation of effective temperature, the SMOS L2 product and both the SMAP L2 products show "dry bias" in the high, cold mountainous area. Because of the more accurate brightness temperature observations viewing at a constant angle and more suitable estimations of single scattering albedo and optical depth, both the SMAP L2 products performed significantly better than the SMOS product.Moreover, comparing with station density of in situ network, station representation is much more important in the evaluation of the satellite soil moisture products. Based on our analysis, we propose the following suggestions for improvement of the SMOS and SMAP product suitability in the mountainous areas: further optimization of effective temperature; revision of the retrieval algorithm of the SMOS mission to reduce the topographic impacts; and, careful selection of in situ observation stations for better representation of in situ network in future evaluations. All these improvements would lead to better applicability of the SMOS and SMAP products for soil moisture estimation to the high elevation and topographically complex mountainous areas in arid regions.