Impact of agricultural development on variation in surface runoff in arid regions: a case of the Aksu River Basin

Abstract

Located in the south of Xinjiang Uygur autonomous region, the Tarim River is the longest inland river in China. Agricultural development, excessive exploitation and low surface water use efficiency in the headstream regions have led to a marked decrease in the water supply to the mainstream. This, in turn, has resulted in the drying-up of the watercourse in the lower reaches of the Tarim River and serious deterioration of the eco-environment. The Aksu River Basin, the most important headstream of the Tarim River, was selected as the research area in this study. Taking elastic coefficient, water demand coefficient and water utilization intensity as the indices, we studied the impact of agricultural development on decreasing surface runoff since the 1950s. The results indicated that (1) the increasing rate of consumption of surface runoff outstripped the rate of increase measured in the natural catchment discharge, resulting in ever diminishing stream discharge into the Tarim River. Agricultural irrigation and seepage loss in irrigation canal systems were the major sources for runoff consumption, taking 63.72% of the overall runoff consumption. What's more, agricultural water consumption took up more than 97% of the water used for long-term production; (2) the expansion of cultivated land, change of planting structure and comparatively low agricultural irrigation efficiency all contributed to the decrease in surface runoff of the Aksu River. The elasticity coefficient of surface runoff reduction corresponding to the increase in planted area was 0.34 in the 1950s, while in the 2000s it had increased to 7.87. This reflected a more sensitive response of runoff decrease to cultivated land expansion. The increase in cotton and fruit production, without widely-used scientific irrigation methods and water-saving technology, led to considerable waste of the water resources. Meanwhile, the irrigation efficiency was still quite low, characterized by the waste of water resources, and the decrease of surface runoff; (3) in different stages, cultivated land area, planting structure and agricultural water use efficiency exerted different effects on runoff decrease. In the early stage, agricultural development showed no obvious effect on runoff decrease. Since the 1960s, the expansion in cultivated land resulted in large consumption of surface runoff; since the 1990s, not only expansion in cultivated land expansion, but also planting structure exerted significant impact on the consumption of surface runoff. Recently, though agricultural water use efficiency has improved in some regions to reduce the consumption of runoff to a certain extent, overall agricultural water use efficiency is still quite low; (4) during the investigation period, water consumption by agricultural development reflected the unbalanced relationship between human activities and water resources.

Comparison of evapotranspiration estimates based on the surface water balance, modified Penman‐Monteith model, and reanalysis data sets for continental China

“…Information on the actual water impoundment of reservoirs is only available for medium-sized and large reservoirs (impoundment data for small reservoirs are lacking), which may also affect long-term trend detection. Second, the water balance method does not consider many other factors that could strongly influence terrestrial water storage levels, such as water withdrawal patterns [Haddeland et al, 2014;Zhang et al, 2012], lake shrinkage/expansion [Ma et al, 2010;Zhou et al, 2015], and glacier melt changes [Bolch et al, 2012;Cogley, 2011;Qin et al, 2006]. The possible impacts of these factors on estimated ET values have been discussed at length [Mao et al, 2016].…”

Characteristics and influencing factors of crop coefficient for drip-irrigated cotton under plastic-mulched condition in arid environment

“…Almost 50 of the total cotton in the TRB is produced in the Aksu Oasis. While annual precipitation amounts only 50 mm on average, nearly all croplands are irrigated and account for over 97 of total water use in the oasis Zhang et al, 2012a . With the expansion of the oasis and the exploitation of the groundwater in recent years, the use and allocation of water resources are now critical elements of the water resources management in the region Han et al, 2015 . Therefore, a comprehensive understanding of K c for cotton will not only optimize the amounts of irrigation water, but will also support the government in the a priori information decision making.…”

Quantitative Detection and Attribution of Runoff Variations in the Aksu River Basin

“…In addition, the expansion of cultivated land area was the most obvious factor related to human activities that has affected the runoff in the Aksu River Basin [52] and it has primarily occurred on both sides of the river downstream (Figure 3). The cultivated land area increased from 965.87 km 2 in the 1960s to 1113.16 km 2 in 1990 and to 1347.67 km 2 in 2013.…”

“…From the 1960s~1990, the cultivated land area increased by approximately 4.91 km 2 /a, whereas from 1990 to 2013, the cultivated land area rapidly expanded to 10.20 km 2 /a (Table 6). In addition, the expansion of cultivated land area was the most obvious factor related to human activities that has affected the runoff in the Aksu River Basin [52] and it has primarily occurred on both sides of the river downstream (Figure 3 (Table 6). …”