The ecological process in the Tarim River, Xinjiang, northwest China, has undergone great changes due to human disturbance over the past 50 years. Most notably, alteration in the spatial-temporal pattern of water resources has resulted in a damaged or degraded vegetative ecosystem in the lower reaches of Tarim River, a condition that restricts local economical development. However, after raising the water level by watering to the lower Tarim River, such ecological degradation was obviously reversed within a certain region of the water channel. Both agricultural production and animal husbandry improved greatly as well. Taking the 35th state farm as an example, the areas utilized or available for farming increased greatly; furthermore, the total value of agricultural production is 1293.13 × 104 US$, increased by 128% (the rate between the increased production and the original one) after adoption of new management of water. Livestock population has experienced a growth trend as a result of water transfer compared before water transfer. The results of this investigation suggest that the reversible state of the eco-environment following watering has had a positive effect on local agricultural development. In addition, we analyzed the relationship between ecological change and agricultural development and discuss water resource management and its ecological significance.The availability of water is an important factor for agricultural production in arid areas. However, excessive utilization of water resources strongly influences local agricultural development and plays a vital role in accelerating environmental degradation. It is very important to efficiently utilize and rationally distribute water resources in arid areas. Some reservoirs and dams are built for agricultural water management, especially in water-short countries. Such engineering projects may promote agricultural development; however, much has been learned during the last several decades about the adverse effects of dams on the physical, chemical, and biological characteristics of rivers). With a deep understanding of sustainable development and the integrity of ecological subsystems, owners and local communities are beginning to face the difficult dilemma of whether to repair, replace or remove reservoirs/dams. Some experts expect to remove them as a means of restoring rivers and degraded ecosystems. There are several examples in arid areas where water resources have been redistributed to meet ecological water requirements through reservoir/dam removal.
This paper uses the water transfer project as a case study to present the effects of eco-environmental change on local agricultural development before and after water transfer to the lower Tarim River, located in Xinjiang, in northwest China, as a result of dam removal. The purpose of dam removal was to redistribute the available water resources to restore degraded ecosystem in the lower reaches of the Tarim River. We quantify the relationship between ecological protection and agricultural production. We also verify the importance of agricultural water management in the fragile ecological areas of the Tarim River.We believe that if we only rely on natural ecological processes of recuperation, it would be difficult or impossible to restore the environment. Water resource management is a necessity for improving the degraded eco-environment in the Tarim River. A population increase and social economic development have caused a decrease in water resources in the lower reaches. Furthermore, some issues still exist in water resources management. First, there is no effective and standard management system. Excessive water resource consumption, severe waste and a scarcity of controlled projects prohibit realization of the sustainable distribution and rational utilization of water resources. Statistical data show that water consumption in the irrigated areas of three headstreams increased from 50 × 108 m3 in 1950 to 155 × 108 m3, an increase of nearly two-fold, whereas water consumption increased from 12.6 × 108 m3 in 1959 to 24.88 × 108 m3 in 2001, an increase of 100%. The water flowing into the lower reaches decreased gradually. Consequently, many ecological problems appeared, as discussed above. It is suggested here that much effort should be devoted to the promotion of scientific and technological progress to protect and manage water resources.
Second, since they are the main agricultural exploitation areas due to the convenience of water resources, the upper reaches usually utilize river-flooding irrigation to grow crops or cotton. The average irrigated ration was 22965 m3/ha in 1998. This is 88% higher than the average irrigative water amount of Xinjiang during the same period, a situation that results in severe soil salinization in the upper reaches. If river channels were reconstructed and a water conservation measure was implemented in the upper reaches, the gross irrigated ratio would decline 10% and could save about 15.51 × 108 m3 of water. If the gross irrigated ratio in the mainstream declined to the average level of Xinjiang, 15.36 × 108 m3 of water would be saved in the mainstream, which is equal to the entire water volume for 5 years of ecological water transfer to the lower reaches.
Finally, soil texture in the middle reaches, mainly composed of sand and clay, is characterized by weak erosion resistance and high water permeability. Rivers with large bend curvatures and many branches deplete 90% of flooding water, resulting in the formation of areas of flooding silt in the middle reaches. Therefore, some rehabilitation measures are suggested, such as the establishment of an engineering project, dam removal, ecological strobes for controlling flood and so on. Fortunately, the local community and the water conservancy department have paid much attention to this issue. The Chinese government allocated 14.3 × 108 US$ toward harnessing the Tarim River in 2000. Some countermeasures have been implemented, such as reconstruction of water conservation engineering projects in headstreams; improvement of water conservation techniques in irrigation areas; moderate exploitation of the groundwater; rehabilitation of the river channel in the mainstream and retransforming farmland into natural forest and grassland. The Daxihaizi Reservoir and some plain reservoirs have been removed gradually as well; thus, implementation of water resource management would probably increase the amount of water flowing from the headstreams to the mainstream in order to satisfy the ecological water requirement along the river channel in the downstream Daxihaizi Reservoir. At the present time, although those countermeasures have not been completely finished, about 7.62 × 108 m3 of water saving in the upper and middle reaches transfers to the lower reaches after harnessing the Tarim River for 7 years. The water transfer project promotes the ecological restoration and rehabilitation in the lower reaches under the precondition of ensuring agricultural production in the upper and middle reaches.
No Comments, Comment or Ping