低纬高原地区降水量资源年际变化的特征时间尺度及其时空演变

应用三维数据的时间小波变换方法,分析研究了低纬高原地区降水量资源在年际变化上的特征时间尺度及其时空演变。结论为:低纬度高原地区降水量资源在年际变化上的特征时间尺度分别约为2 a、7 a和15 a。2 a、7 a和15 a特征时间尺度的较大振幅能量活动区,分别主要位于滇西北到滇东南、滇东北到滇西南和滇中一带。与2 a特征时间尺度相对应的较大振幅能量活动中心纬度的降水量,表现出了明显的东西向波动的时间演变特征,而与7 a和15 a特征时间尺度相对应的较大振幅能量活动中心纬度的降水量,则表现出了在东西向较为稳定少变的时间演变特征。与2 a特征时间尺度相对应的较大振幅能量活动中心经度的降水量,也表现出了明显的南北向波动的时间演变特征,而与7 a和15 a特征时间尺度相对应的较大振幅能量活动中心经度的降水量,则表现出了一种明显向南移动的时间演变趋势。

An Improved Markov Chain Model Based on Autocorrelation and Entropy Techniques and Its Application to State Prediction of Water Resources

According to the relationships among state transition probability matrixes with different step lengths, an improved Markov chain model based on autocorrelation and entropy techniques was introduced. In the improved Markov chain model, the state transition probability matrixes can be adjusted. The steps of the historical state of the event, which was significantly related to the future state of the event, were determined by the autocorrelation technique, and the impact weights of the event historical state on the event future state were determined by the entropy technique. The presented model was applied to predicting annual precipitation and annual runoff states, showing that the improved model is of higher precision than those existing Markov chain models, and the determination of the state transition probability matrixes and the weights is more reasonable. The physical concepts of the improved model are distinct, and its computation process is simple and direct, thus, the presented model is sufficiently general to be applicable to the prediction problems in hydrology and water resources.

Stable Isotopes in Precipitation in Xilin River Basin,Northern China and Their Implications

Under the increasing pressure of water shortage and steppe degradation, information on the hydrological cycle in steppe region in Inner Mongolia, China is urgently needed. An intensive investigation of the temporal varia-tions of δD and δ^18O in precipitation was conducted in 2007-2008 in the Xilin River Basin, Inner Mongolia in the northern China. The 6D and δ^18O values for 54 precipitation samples range from ＋1.1%o to -34.7%0 and -3.0%0 to -269%0, respectively. This wide range indicates that stable isotopes in precipitation are primarily controlled by differ-ent condensation mechanisms as a function of air temperature and varying sources of vapor. The relationship between δD and δ^18O defined a well constrained line given by δD = 7.896180 ＋ 9.5, which is nearly identical to the Meteoric Water Line in the northern China. The temperature effect is clearly displayed in this area. The results of backward tra-jectory of each precipitation day show that the vapor of the precipitation in cold season （October to March） mainly originates from the west while the moisture source is more complicated in warm season （April to September）. A light precipitation amount effect existes at the precipitation event scale in this area. The vapor source of precipitation with higher d-excesses are mainly from the west wind or neighboring inland area and precipitation with lower d-excesses from a monsoon source from the southeastern China.

Climate Change and its Impact on Water Resources in the Huai River Basin

Rainfall and air temperature data from six meteorological stations above the Bengbu Sluice and hydrological and water resources evaluation data from the Bengbu Hydrological Station in the Huai River Basin from 1961 to 2008 are used to analyze the impact of changes in climatic factors on the amount of water resources in the Basin. There was a general trend of rise in its average annual air temperature, with the highest increase of 0.289℃/10a recorded at Bengbu in Anhui Province. Rising rainfall was mainly observed in the western part of the study area, while rainfall actually declined in the eastern part, i.e. the middle reaches of the Huai River. The Average rainfall in the study area was in a vaguely declining trend. In other words, the rainfall in the Basin is still much affected by natural fluctuations. On the whole, there was a trend of gradual decrease in the quantity of the Basin＇s water resources for the period under study. Water resources quantity is found to fall with decreasing rainfall and rising air temperature. Regression analysis is used to establish a mathematical model between water resources quantity and climatic factors （i.e. air temperature and rainfall） in order to explore the impact of climate change on water resources in the Basin. Moreover, various scenarios are set to quantitatively analyze the response of water resources to climate change. Sensitivity analysis shows that changes in rainfall have a much bigger impact on its water resources quantity than changes in its air temperature.

Groundwater in Thailand

This article offers a brief description of the water resources situation of the Kingdom of Thailand, a country with a population of over 65 million people and a surface area of 513,120 km^2. The average annual rainfall is 1,430 mm and the total water resources are estimated at 215,000 Mm^3 （million of m^3）-year^-1. The hydric demand in the country is 70,000 Mm^3.year^-1, 6% of which is groundwater in origin. Over 70% of the water is used for agriculture. Thailand is the world＇s leading exporter of rice. The main problems faced by the Water Authority in Thailand are pollution, floods and droughts, depending on the geographical zone. From the hydrogeological point of view, the Central Plain is the main groundwater reservoir in the nation. Intensive extraction of groundwater over a long period of time has caused three main problems： a decline in groundwater levels, land subsidence, and seawater intrusion. These problems have been especially pressing in the area known as Greater Bangkok.

Inter-annual variation of streamflow,precipitation and evaporation in a small humid watershed(Chengcun Basin,China)

For sustainable water resource management,it is important to determine the relationship between streamfl ow and other variables that infl uence availability of water resources.However,many catchments do not have suffi cient data to allow for a more detailed study of these relationships.We faced a similar challenge in the Chengcun Basin(limited historical data: from 1986–1999); and therefore we used a new approach to overcome this.We found that,using nonparametric trend methods in conjunction with the climate elasticity analyses and the 2D visualization of hydrologic data,it is possible to assess the relationships between streamfl ow and other hydro-climatic variables.In the past,streamfl ow trends in the basin were more correlated with precipitation than with potential evapotranspiration(PET).In addition,there is a gradual shift in the hydrological regime of the catchment,which may affect the occurrence of available water resources and activities that depend on them.In addition,based on our climate sensitivity analyses,the streamfl ow is dependent and more sensitive to variations in precipitation than to PET(δQ=0.79δP+0.42δE; precipitation elasticity,ε P=1.32; PET elasticity,ε E=-2.10).Therefore pending more detailed studies,the use of our approach will provide a rapid means to assess the variation of water resources(streamfl ow)in a watershed.In the future,we hope to carry out related research in other watersheds and also perform a more detailed studies to improve upon the results of this study.