Search

[ABSTRACT] North China Plain (NCP) is the main granary in China, however, NCP is confronted with water shortage problem that may lead to the fall of the crop production. Thus monitoring NCP from space is very important to know how hydrologic environment affects the crop production. NCP has been monitoring by using NOAA/AVHRR for vegetation conditions. As a result, it is clarified that surface hydrological conditions clearly affect the crop production rate revealed by NDVI. Then the surface wetness is estimated by NOAA/AVHRR and GMS/S-VISSR. The slope parameter in the scattergram between vegetation index and surface temperature is examined for NOAA/AVHRR data. The difference in brightness temperatures between 8:00AM and 10:00AM (LT) is also investigated for GMS data. Both of which are considered to be the index of surface moisture condition. The distributions of surface wetness obtained from both methods well agree with each other. The results will be used for water management such as proper irrigation practice.

[ABSTRACT] The purpose of this study is to clarify the effect of land use changes on the water balance in humid tropics catchment area. The Ciliwung-Cisadane watershed of West Java, Indonesia, is selected as study area where intensive land use changes have occurred in the recent past. The elements of water balance such as precipitation, runoff and evapotranspiration into and from the catchment were estimated independently with data obtained from direct measurement or model calculation. Based on the observation data, there was an increase in runoff ratio of Ciliwung River and Cisadane River about 5-0x1.fc1bp+0nd 4% respectively. It indicates that there are some natural or artificial changes of land use that disturb the river's flows and other water cycle components such as evapotranspiration. Satellite remote sensing data of 1984 and 1991 are used to reveal the land use changes. As results, there recognized large amount of change from paddy to cropland allocation and new settlement areas have been developed on paddy and cropland area respectively. Characteristic values of albedo are assigned to land use classes, and areal evapotranspiration of two periods are calculated by using Penman (1948) equation. As results, the amount of evapotranspiration in 1984 and in 1991 were 1,123mm and 1,010mm respectively, which decreased in the amount of 113mm (10%). According to calculation of water balance, the large amount of residue, which is termed as loss, has been found. These values indicate the possibility of the existence of percolation into deeper layers and the change in water storage.

[ABSTRACT] Groundwater is one of major water resources in the North China Plain (NCP). The area from Taihang Mountain to Buohaiwan along 38°N latitude in NCP has been chosen to analyze the evolution of groundwater quality. In viewpoint of water cycle, the authors of present paper paid careful attentions to the fact that the basic characteristics of groundwater qualities are in close relation to groundwater flow system. It was found that groundwater quality changed from Ca-HCO_3 type to NaCl type, which matches well with groundwater flow direction from recharge area to discharge area. Based on the results of groundwater usage as well as chemical analysis, it is clearly that both nature and human activities effected greatly on the groundwater quality in NCP.

[ABSTRACT] In the Nobi Plain, temperature profiles were measured in 41 observation wells in 1993 and 1994. There are many temperature inversions in the vertical temperature profiles of recharge area. In the Nobi Plain, annual mean surface temperature increases about 2℃ during last 100 years, and it is assumed that this surface warming causes subsurface temperature inversions. A three-dimensional numerical model of heat transfer in the Nobi Plain is used to investigate the influence of surface temperature warming outside the discharge area, where inversions are evident in the measured temperature profiles. Simulated results show that subsurface temperature inversions are formed in recharge area at depth between 50m-130m below sea level, because subsurface temperature has been cooled with the advective heat transfer by the downward groundwater flow from the surface. On the other hand, shallow subsurface temperatures in the center part of the plain have been heated more by upward regional groundwater flow than by the effect of surface warming, so that temperature inversions are not observed.

By transferring natural vegetation with soil from high elevation to low elevation, a 2 degrees C warmer condition was created. In each site, 5 different precipitation treatments were applied to test if the temperature and precipitation changes under global warming will result in a lower soil moisture condition and, therefore, feedback negatively on vegetation productivity of the Taihang Mountain. Two years' field experiment suggested that, because of the low adaptability of Arundinelia hirta under a warmer condition, its productivity decreased significantly at the end of the experiment. Productivities of grass with better adaptability such as Themeda japonica and Artemisia sacrorum did not change significantly between the two sites. Tested vegetation demonstrated a significant increase in productivity under the higher precipitation condition by showing 22% increase in productivity under 20% higher precipitation treatment. Soil moisture condition under treatments with higher precipitation was generally higher than that under treatments with lower precipitation. In the warmer site, soil moisture became higher since the beginning of the second year.