晨漱天河水 涓涓度长年

三国时期有位百岁老人名叫皇甫隆,曹操曾向他请教长寿之术。他说,“要想寿命延,朝朝服玉泉”。玉泉乃唾液也。古人也称为“天河水”、“金津玉液”、“甘露”、“玉泉”。唐代名医孙思邈在《养生铭》中说,“晨兴漱玉津”可祛病益寿。他每天早上醒来,用舌搅出唾液,缓缓咽下,活了一百零一岁,晚年仍从事著述未尝释卷。”

Oasis System and Its Reasonable Development in Sangong River Watershed in North of the Tianshan Mountains,Xinjiang,China

Under the guide of system theory, taking the oasis in the Sangong River watershed as a case study, this paper analyzes the oasis structure and function from 4 aspects including oasis spatial structure, water resources structure, vegetation structure, economic structure and their corresponding functions. The results indicate that as a typical small-scale watershed, Sangong River watershed has the relatively complete mountain-basin structure, and ecological and productive function. Because of human drastic activity the utilization rate of water resources was as high as 98.7%, and the utilization of groundwater was not reasonable, which resulted in an average annual decline of 0.353m in the water table of alluvial-diluvial-fan oasis, and an average annual increase of 0.047m in the alluvial-plain. The layout of crop and shelter forest benefits to the utilization of water and land resources. The development of oasis economy is at low level, and its eco-economic function is weak.

The Changes of Water Quality in Space and Time in the Mekong River, Bassac River and Adjacent Waterways

Catfish （Pangasianodon hypophthalmus） farming along Mekong river and Bassac river depends heavily on water quality of the two rivers, whereas water quality of these rivers are affected by the waste of aquaculture activities, agricultural production, industrial and municipal waste. This report analyzes the monitoring data on Mekong river, Bassac river and adjacent waterways in the period of 2011-2012, focusing on parameters of organic pollution to assess the current quality of these two rivers. Based on the results, the water quality in the river-head was generally better than in the middle and at the end of the river, and the quality of water of the Mekong river was better than Bassac river. In terms of time, water quality in July was considered the best in all the basins. At adjacent natural rivers and canals, ammonia levels increased and exceeded the Vietnamese standard in April, and BOD values were also much higher compared to two major rivers. The results of the model also showed that the levels of pollution index of the Mekong and Bassac river were very low （1.33 and 1.47）, and the values （Y） in the canals were higher （1.63-1.67） but still in permitted level. Therefore, the water quality of the Mekong and Bassac river in the period 2011-2012 was generally still quite good.

A type of dynamic mechanism of river hydraulic geometry

Large-sczde structure of river flow is the main driving force for bed erosion-deposition and bank delbrmation. The structure shapes and retains a corresponding hydraulic geometry form. Therefore, the most stable flow structure is the probable natural river plane formation. Natural coordinate transformation and perturbation methods were adapted to deform the governing equations of sine-generated river basic flow and disturbance flow independently. The stability and retention of perturbation waves were analyzed in our model to explain why meandering rivers followed a certain type of tqow path. Computation results showed that all types of perturbation waves in meandering rivers were most stable when the meandering wave number was about 0.39-0.41. We believe that this type of stable flow structure shaped a certain meandering river. The statistical average length-width ratios of Yalin, Habib and da Silva and Leopold and Wolman somewhat confirmed our most stable river mean- dering wave number. In some ways, meandering rivers always tend to diminish internal turbulence intensity.

High-quality reconstruction of China’s natural streamflow

Reconstruction of natural streamflow is fundamental to the sustainable management of water resources.In China,previous reconstructions from sparse and poor-quality gauge measurements have led to large biases in simulation of the interannual and seasonal variability of natural flows.Here we use a well-trained and tested land surface model coupled to a routing model with flow direction correction to reconstruct the first high-quality gauge-based natural streamflow dataset for China,covering all its330 catchments during the period from 1961 to 2018.A stronger positive linear relationship holds between upstream routing cells and drainage areas,after flow direction correction to 330 catchments.We also introduce a parameter-uncertainty analysis framework including sensitivity analysis,optimization,and regionalization,which further minimizes biases between modeled and inferred natural streamflow from natural or near-natural gauges.The resulting behavior of the natural hydrological system is represented properly by the model which achieves high skill metric values of the monthly streamflow,with about 83%of the 330 catchments having Nash-Sutcliffe efficiency coefficient(NSE)>0.7,and about56%of the 330 catchments having Kling-Gupta efficiency coefficient(KGE)>0.7.The proposed construction scheme has important implications for similar simulation studies in other regions,and the developed low bias long-term national datasets by statistical postprocessing should be useful in supporting river management activities in China.

A surface-based hiding function linking flume and field data

The quantification of the sheltering and exposure effects of non-uniform sediments has been widely achieved through hiding function models. Big challenge exists so far in the model parameter that is highly variable and differs greatly between laboratory flumes and field streams. This paper presents an improved surface-based hiding fimction. The force balance for particle inception was formulated and the allocation of the overall bed shear stress into each group of sediments was mimicked. The new hiding function was examined against and agrees well with the documented field and flume data. It was shown that the hiding fimction is closely related to the relative flow depth and the reference elevation in the velocity profile in addition to the bed material gradation. The power law of velocity profile that applies to both flume flows and natural streams can link the flume and field data together. The hiding function with b = 1/6 and b = 1/2 is applicable to natural streams and laboratory flumes, respectively. The value orb = 0.263 also works well for gravel bed rivers. The range of the reference elevation, namely z0 = 0.4Dm-1.4Dm, is recommended for either the flume or field data. The new hiding function contributes to addressing clearer physical meanings and a useful perspective for further improvement.