Song Yu-dong

The utilization of water resources and its variation tendency in Tarim River Basin

Water resources efficient utilization is the key to ecological improvement and economic development in Tarim River Basin. It is necessary to analyze the water resources utilization and its variation tendency in the whole river basin. Based on the monitored data and formation at eight meteorological stations and fifteen hydrological stations, the method of time series, regression analysis are applied to analyzing the water resources utilization and variation trend in the headstreams and mainstream areas especially in recent 10 years. The quantitative results indicate that inflows of the headstream areas have an increasing trend to different extent in the past 40 years. The runoff increasing trend is more significant from 1994 to 2002, which show the water resources condition in the headstreams is at an advantage. However, under the condition of water increase with the volume of 25×108 m3 in headstreams in recent 10 years, the mainstream water flowing from the headstreams has increased less than 0.9985×108 m3. In addition, the runoff at the different hydrologic stations along the Tarim River has a significant linear decreasing trend. It is shown that the degraded trend of ecological environment in the mainstream areas hardly changes even if the Tarim River Basin is in the special water period for ten consecutive years.

The dynamic variation of water resources and its tendency in the Tarim River Basin

The method of time series is applied to analyze the variation of precipitation and temperature from 1961 to 2002 in the mountainous areas of the Tarim River Basin, as well as water consumption in the headstream and mainstream areas. Those hydrologic parameters are verified. Quantitative results indicate that the precipitation and temperature in the headstream areas have an increasing trend to different extent. The increasing trend of precipitation is less significant than that of the temperature (α= 0.05). Runoff of three headstreams also increases especially from 1994 to 2002. Compared with the perennial runoff, the annual runoff has increased by 25.163 × 108 m3/a. However, inflows of the mainstream areas has only increased by 0.9985 × 108 m3/a. So the runoff at the different hydrologic stations in the headstream areas has a linear decreasing trend. It is shown that the degraded trend of eco-environment of the Tarim River Basin hardly changes in the special water period for ten consecutive years. Given runoff of three headstreams is accounted in normal period from 1957 to 2003, the annual runoff of the headstream areas would be only 22.57 × 108 m3. Therefore, more attention should be given to ecological safety of the Tarim River Basin.

Suitable scale of Weigan River plain oasis

Desert coexists with oasis in long time, and the existence and development of oasis system demand better oasis vegetation ecological system. Oasis scale of arid zone plain encircling water should be determined in case of desertification caused by land over-reclamation under the circumstance of water resources shortage. Steady oasis with virtuous circle must have appropriate land use structure for agriculture, forestry and graziery. The study on the suitable scale and developmental space of oasis will provide theoretical and applicable foundation for effective construction of oases. By analyzing the hydrothermal, water and soil balance, an optimal mathematical model has been established. Based on hydrometeorology data collected for years in Weigan River plain, and by the principle of water balance, a calculation has been made of the water resources for evapotranspiration and the optimal acreage of oasis and cultivated land, which shows that the water resources for evapotranspiration in the Weigan River plain oasis is 22.32×108 m3 and the optimal oasis acreage under the condition of conventional irrigation mode is 3716.06 km2, in which the suitable cultivated land acreage is 1564.79 km2. Under the condition of water-saving irrigation, the suitable oasis acreage is 5515.49 km2, in which the suitable cultivated land acreage is 2322.31 km2. The oasis area had reached 4123 km2, and the cultivated land acreage had reached 1507 km2 after the Agriculture Irrigation Drainage Water Project of World Bank Loan in Weigan River basin was finished in 1997. The oasis and cultivated land acreage will be more suitable, and the oasis scale can be enlarged moderately by means of water saving irrigation.

Models for calculating phreatic water evaporation on bare and Tamarix-vegetated lands

Groundwater is the main source of water consumption of natural vegetation in arid regions. It is an effective approach to study ecological water demand of natural vegetation by phreatic evaporation. In order to study the ecological water demand of Tarim river basin, based on the observation data of phreatic evaporation on bare lands at the Aksu Water Balance Experimental station from 1989 to 1996, by analyzing the relationship of phreatic evaporation, depth of phreatic surface and evaporation of water, taking the limit rate of phreatic evaporation as the control condition, and based on the objective law that the relation between phreatic evaporation and evaporation of water is nonlinear, we establish models for calculating phreatic evaporation on bare land, which can fully reflect the law of phreatic evaporation in the Tarim river basin. According to the data of depth of phreatic surface and soil moisture when pheratic level decline is caused just by evapotranspiration on Tamarix-vegetated land from 2003 to 2004, we calculate the amount of phreatic evapora-tion and set up models for calculating phreatic evaporation on Tamarix-vegetated land. Phreatic evaporation on bare land and Tamarix-vegetated land could be transformed each other by a Tamarix vegetation conversion coefficient. The test results show that the calculation accuracy of the models is high and the models are suitable for Tarim river basin.

Eco-water conveyances applied to control desertification at the lower reaches of the Tarim River

The lower reaches of the Tarim River are one of the areas suffering from most severe sandy desertification in Xinjiang, Northwest China. Irrational utilization of water and land resources results in eco-environmental deterioration in the Tarim River. In May 2000, the local government carried out the water conveyances project in the Tarim River. The influence of water conveyance on desertification reversion is analyzed and discussed according to the monitoring data in the past three years. Based on monitored data of the nine observed sections, along the channel of conveyance, the intensity and scope of desertification reversion in the upper reaches are larger than those in the lower reaches. Dynamic changes of desertification reversion are more obvious from the channel of conveyance to its two sides. However, the range of influence and intensity of desertification reversion is limited at present. It is suggested that the way and range of water conveyances should be adjusted in the future.

CHARACTERISTICS OF WATER TRANSFORMATION AND ITS EFFECTS ON ENVIRONMENT IN THE ARID REGION —A case study in Alar irrigation region of Xinjiang, China

The characteristics of water balance in arid regions is that the streams are formed in mountain area and continuously evaporates and infiltrates in the process of flowing to plain area, streams finally disappear in the desert or flow into the lakes, which are the low reaches of the rivers. But the distribution and transformation of water in Xinjiang, China have changed under the influences of human activities. The influences of human activities take place in a short time and regionally, especially in arid land where water is the key factor of environment. Water inside of oasis has increased, and water out of oasis or at the lower reaches of the river has decreased. Human activities have caused the environment changes in both positive and negative aspects by changing the circulation and distribution of water. Under the influence of human activities, oases in Xinjiang have expanded, meanwhile some lakes have contracted desertification is serious, natural vegetation has declined and natural environment out of oasis has degenrated.