River's life is a process of hydrologic cycle which is carried out under certain direction and path, and represented by continuous flow in the river channel. Continuous water circulation is the key to keep the life of a river. The concept of river health is the description of river life status, and the river health conditions reflect human judgments on contributions of rivers to human society, or whether the river could function well to meet the requirement of people. The standard of river health is the balance or compromise of human benefit and other biological benefit in corresponding times and river reaches. By analyzing the requirements of mankind and river ecosystem, the healthy Yellow River symbols have been developed which are continuous flow, favorable riverbed, favorable water quality, acceptable river ecosystem and certain water supply capacity. Eight parameters, such as minimum flow, maximum flood discharging capacity, bank-full discharge, floodplain transversal slop, water quality degree, wetlands area, aquatic organisms and water supply are the vivid descriptions of healthy YR situation, and their ideal standards have been proved.
Based on the data from the Yangtze Water Resource Committee and the estimation of the sediment supply from the ungauged area in the Yangtze Water basin, this paper established a sediment budget of the Yangtze River and studied the responses of the main river channel to the water and sediment supply in the Yangtze basin and the effects on the sediment supply to the sea. The results show that the average accretion velocity of river channel in the Pingshan-Datong section is 88.58×106 t/a, which is 14% and 21% of the total sediment supply from the basin and sediment discharge at Datong station respectively; sediment discharge at Datong station decreases by 17.5% because of the deposition in the main river channel, which is moderate in the upper reach and serious in the middle reach; slight erosion occurs in the Hankou-Datong section. Generally, the erosion/accretion amount has significant relationship with the total sediment supply from the basin but responses of each section of the river channel are quite different. Neither the water nor the sediment discharge has significant relationship with the erosion/accretion amount at the upper reach. The erosion/accretion amount has significant relationship with the total sediment supply in the Yichang-Hankou section and with water discharge at Datong in the Hankou-Datong section. The impoundment of the Three Gorges Dam (TGD) has effectively changed the erosion/accretion pattern of the main channel of the Yangtze.
The present study analyzed the temporal and spatial changes of groundwater quality from 1982 to 2004 in Xiaojiang watershed, Yunnan, Southwest China. The results indicate: (1) There were obvious temporal and spatial changes of groundwater quality in Xiaojing watershed from 1982 to 2004. The total hardness, total alkalinity, pH, Mg2+, NH4+, SO42-, Cl-, NO3- and NO2- of the groundwater increased significantly, but the Ca2+ and HCO3- showed an obvious declining trend during the past 20 years in Xiaojiang watershed. Furthermore, the concentrations of NH4+, NO3- and NO2- of groundwater exceeded the drinking water standards in 2004. (2) The total land transformed covers 610.12 km2, of which 134.29 km2 of forestland were transformed into cultivated land, and 210 km2/sup> of unused land was transformed into cultivated land, and the construction land increased by 71.8% during the past 20 years in Xiaojiang watershed. (3) The groundwater quality change is related to the non-point pollution of massive use of fertilizers and pesticides due to the expansion of cultivated land and the deterioration of eco-environment bought by the worsening of forestland quality. As forestland and unused land transformed into cultivated land, the total hardness, total alkalinity, pH, and the concentrations of NH4+, SO42-, NO3-, NO2-, and Cl- in the groundwater increased significantly, but the concentrations of Ca2+ and HCO3- in the groundwater declined obviously.
The Tarim River Basin, a river system converged by nine source tributaries, is the mostly glacierised watershed in the arid northwest China, where there are 11665 glaciers with a total area of 19878 km2 and a volume of 2313 km3. Glaciers in the basin play a significant role in the water resource formation and variations. An estimation indicated that glaciers provide meltwater of about 133×108 m3 every year, taking 39% of the total river runoff. With the influence of global warming, northwest China has experienced a general warming and drying change of climate since the mid-19th century. However, a so-called “warm and wet transition” of climate in the region has occurred since the late 1980s, exhibiting as an increase both in precipitation and outlet discharge in Xinjiang and neighborhood regions. This paper attempts to reveal how glaciers in the Tarim River Basin response to such a warming and wetting change and what impact glacier changes exert. We analyzed the variations of more than 3000 glaciers since the 1960s by applying topographical maps, high resolution satellite images and aerial photos for the river basin. Results indicate that glaciers in the basin has been mostly in retreat in recent 40 years, and the ice wastage have significantly influenced the variations of water resources in the Tarim River Basin.
Ateaoyinake River, located on the southern slope of the Tumer Peak in the western Tianshan Mountains in China, is the largest modern glaciation center. Six relative integrated sets of glacial tills formed in Quaternary glacial-interglacial cycles were reserved in this area. ESR dating technique (OSL dating technique as a supplementary method) was applied to determine the ages of the glacial tills and outwashes. The dating results of the six glacial groups are 7.3±0.8 ka BP (OSL, outwash sand), 12.3±1.2 ka BP (OSL) and 15-29 ka BP, 46-54 ka BP, 56-65 ka BP, 155.8±15.6 ka BP and 234.8±23.5 ka BP, 453.0±45.3 ka BP respectively, indicating that they deposited in Neoglaciation, MIS2, 3b, 4, 6 and 12. The results of the third set of the glacial tills demonstrate that a larger glacier advance happened in MIS3b in this area, similar with the extent of the Last Glacial Maximum (MIS2). The age of the oldest glacial tills consistent with the ESR ages (459.7±46 ka BP and 477.1 ka BP) of the Gaowangfeng glacial tills at the headwaters of the Urumqi River, demonstrating that the western and the middle sections of Tianshan Mountains entered cryosphere at least in MIS12, resulting in development of the glaciers in that period.
Based on the data of δ18O in surface snow, snow pits, meltwater and the glacier-fed river water at Baishui glacier No. 1, Mt. Yulong, the isotopic fractionation behaviors in the typical monsoonal temperate glacier system in winter and summer were compared. The results indicate that the isotopic fractionation degree in summer is larger than that in winter, suggesting that the snow/ice melting is more intense in summer. Moreover, whenever it is in winter or summer, from surface snow to meltwater, and to glacier-fed river water, the gradient of δ18O with altitude gradually increases. It shows that the degree of isotopic fractionation gradually strengthens when surface snow being converted into meltwater and finally into glacial river water, which suggests that the influence of post-depositional processes on δ18O gradient in the monsoonal temperate glacier region differs spatially.
Inland lake is a sensitive indicator of climate change. Because lakes in high mountain region are in natural status and are little affected by human activities, their changes can reflect climate conditions. In this paper, four inland lakes (Bamucuo, Pengcuo, Dongcuo and Nairipingcuo) area changes in area and factors causing the water level growth are analyzed using remote sensing data and climate data from meteorological stations near the four lakes. For lake area changes from 1980 to 2005, the TM and CBERS remotely sensed data and topographic map at 1:100,000 scale in 1975 are used in this study. The meteorological data including temperature, rainfall, evaporation (1971-2004), snow depth and land frost depth from four meteorological stations Naqu, Anduo, Bange and Dangxiong which are the closest to the four lakes are used in this study. Based on the lake area information derived from a digitized 1:100,000 scale topographic map in 1975 and satellite remote sensing data from 1980 to 2005 georeferenced using topographic map, it is found out that four lakes' areas increased in 1980 compared with 1975, by 9.8 km2, 9.7 km2, 12.9 km2 and 3.9 km2, respectively. In 1988, the four lakes retreated and their areas are equivalent to the areas in 1975. The areas of Bamucuo, Pengcuo, Dongcuo and Nairipingcuo notably increased during the last 30 years from 1975 to 2005. Their areas increased by 48.2 km2 (25.6%), 38.2 km2 (28.2%), 19.8 km2 (16.2%) (compared with 2004) and 26.0 km2 (37.6%). The lake area increase has been more obvious since 2000. The analysis of climate changes for the last 40 years shows that annual mean temperature and precipitation increased significantly, while evaporation, maximum land frost depth and maximum snow depth decreased. For instance, the mean temperature increased by 0.28 oC/10a from 1961 to 2004; rainfall witnessed a big fluctuation from 1961 to 1994 and the maximum and minimum rainfall occurred in this period. The rainfall has been increasing since 1994. Evaporation decreased by 130 mm/10a from 1995 to 2004. The maximum land frost depth reduced 10 to 40 cm and the maximum snow depth decreased as well. The result based on the relationship between lake area changes and climate variation shows the main factors which are directly related to lake water level are rainfall, ice snow defrost and land frost. The indirect factors of lake area changes are temperature, lake size, catchment's area, land formation of lake basin, surface features etc.
Air temperature in the Lhasa River basin has increased by 0.54oC since 1990, particularly in winter and autumn, while precipitation did not increase in the same period. Based on climatological data of (1963-2003) and monthly runoff data of 28 years (1976-2004), the hydrological and geoCryological response to the climate change was studied. The significant response to the temperature rising from the winter streamflow during November to February was detected, winter streamflow during December to February increased by 16% and in February by 22%. Correlation analysis between water flow and temperature indicated that the rise in temperature in oCtober and November by 0.8-0.9oC resulted in the increase in winter streamflow, the seasonal frost at depth of 0.9-1.5 m became thinner comparing with that before the 1990s, the thickness decreased by about 14 cm. The hydrological response from winter flow in a permafrost basin is more sensitive and quicker than that of air temperature. There are un-certainties due to the lack of both soil frost and snowfall survey on the Tibetan Plateau.
Using foggy days and mean temperature and relative humidity of 602 stations from January to December in the period 1961-2003 in China, the relationship between variations of foggy days and temperature and its possible reason for 43 years were analyzed by regression, correlation and contrastive analysis methods. The results show that the higher (lower) the mean temperature and relative humidity, the lower (higher) corresponding to the less (more) foggy days, the relationship is best in the western, northern, eastern Sichuan, the Yunnan-Guizhou Plateau, and southeast highland in China. This induces a decrease in relative humidity when the climate becomes warmer, and eventually brings about a decrease in foggy days in China.
The Pearl River estuary system consists of a complicated stream network and estuarine bays, the two portions of the estuary system are connected by 'men' (meaning 'gate' in Chinese), a special morphological unit. During the last transgression, the ancient Pearl River estuarine bay was separated into inner and outer bays by a series of rocky islands. The brackish water of inner and outer bays is connected at only several locations through rocky gorges which became 'gates', the outlets of the network system. Based on hydrographical investigations, bore hole data, topographic maps and with the application of the long-term morphodynamic model PRD-LTMM on the delta evolution since 6000 aBP, the present a morphodynamic study focuses on (1) bi-direction jet system of modern 'gate', (2) evolution of 'gate', (3) effect of 'gate' on tidal energy convergence, (4) coupling development of 'gate' with the associated Pearl River Delta plain, and (5) mechanism of 'gate' on the formation of the network system. Mainly due to the geological constraint of the coast and the effects on the re-distribution of marine and river energy, the evolution of the Pearl River Delta and estuary system is unique among the large scale delta and estuary systems in the world.
Based on the existing data of the Yangtze delta area, a preparatory simulation has been done by the model on the Holocene geomorphic evolution in the Yangtze delta area, and a good simulative effect has been observed from the paleotopographic maps, which are generated from the model. The simulation shows that (1) the coastline evolution can be divided into three stages by taking 3000 aBP and 7000 aBP of the Holocene as a divide, the early stage is a rapid transgression stage, the middle stage is a transgression-regression repeated fluctuating stage and the late stage is a transgression stage; (2) the core region of the Taihu lake plain maintained basically a land environment all through the Holocene, not being suffered from large-scale transgression. But it is quite possible that transgressions have happened in the western part of the Taihu lake plain and part of the Taihu lake basin. In order to validate the simulation modeling, we have conducted qualitative and quantitative analyses from different aspects using data of the 304 archaeological sites in different cultural periods and the 73 14C dating data corrected by tree-ring. The validation results showed that the simulation method is a preferably reliable one to reconstruct the Yangtze delta geomorgraphic evolution and the simulation results are believable. So this study has set up the model simulation experimental method based on the GIS/DEM technology, which can be used to reconstruct and inverse the delta geomorgraphic evolution.
