Science of the Total Environment 663 (2019) 315–328 Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv Climate background, relative rate, and runoff effect of multiphase water transformation in Qilian Mountains, the third pole region Zongxing Li a,⁎,RuifengYuana, Qi Feng a,⁎, Baijuan Zhang a, Yueming Lv a,YonggeLia,WeiWeic, Wen Chen b, Tingting Ning a,JuanGuia, Yang Shi a a Key Laboratory of Ecohydrology of Inland River Basin/Gansu Qilian Mountains Eco-Environment Research Center, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China b Gansu Provincial Hydrographic Resources Bureau, Lanzhou 730000, China c Research Center for Eco-Environment Sciences, Chinese Academy of Sciences, Beijing 100085, China HIGHLIGHTS GRAPHICAL ABSTRACT • Finding the lengthening ablation period and the larger warming in cryosphere belt. • Glaciers area retreat rate has accelerated by 50% after 1990. • The percent of snowfall accounting for precipitation has decreased by 7% after 1990. • Contribution from the recycling mois- ture to precipitation has increased by 60%. • The outlet runoff increased and seasonal pattern changed. article info abstract Article history: Multiphase water transformation has great effects on alpine hydrology, but these effects remain unclear in the third Received 18 September 2018 pole region. Taking the Qilian Mountains as an example, the climate background and relative rates of multiphase Received in revised form 7 January 2019 water transformation were analyzed, and the runoff effect was evaluated based on long-term field observations. Accepted 25 January 2019 There are three climatic aspects driving multiphase water transformation, including lengthening ablation period, accel- Available online 28 January 2019 erative warming after 1990, and larger warming in the cryosphere belt than in the vegetation belt. The accelerative fi Editor: Ralf Ludwig multiphase water transformation was quanti ed by three facts: the glacier area retreat rate accelerated by 50% after 1990, the percentage of snowfall in precipitation decreased by 7% after 1990, and the contribution from recycling mois- Keywords: ture to precipitation increased by 60% from 1961–1990 to 1991–2016. Under the multiphase water transformation, the Multiphase water transformation outlet runoff for three inland rivers increased by 5 × 108 m3/10 a after 1990. This runoff increase was concentrated Climate warming mainly in the ablation period. For the seasonal runoff pattern, maximum runoff lagged maximum precipitation by Cryosphere one month under increasing glacier snow meltwater and thickening permafrost active layer. Meltwater from the Runoff effect cryosphere is a crucial runoff component in the Qilian Mountains. At present, these multiphase water transformations Qilian Mountains are accelerating, along with the yearly runoff increase, which will obviously have a profound impact on water resources management and flood control in the third pole region. © 2019 Elsevier B.V. All rights reserved. ⁎ Corresponding authors at: Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, China. E-mail addresses: [email protected] (Z. Li), [email protected] (Q. Feng). https://doi.org/10.1016/j.scitotenv.2019.01.339 0048-9697/© 2019 Elsevier B.V. All rights reserved. 316 Z. Li et al. / Science of the Total Environment 663 (2019) 315–328 1. Introduction area, during the past several decades (Cheng and Jin, 2013), which has changed the water cycle and yearly runoff variation (Yao et al., 2013). In the third pole regions, the prominent hydrological feature is the Based on continuous observations from 8 stations along the Qinghai– existence of multiphase water and its transformations (Li et al., Tibet road, the average permafrost active layer depth increased from 2019a). Solid water reserves include glaciers, snow, and ground ice, liq- 252 cm in 2006 to 276 cm in 2011, with an average rate of increase of uid water mainly includes river water, lake water, marsh water, soil 4.7 cm/a (Liu et al., 2014; Li et al., 2019a). Data from 16 stations in Qing- water, plant water, and groundwater, and gaseous water includes hai Province showed that the maximum freezing depth decreased con- local recycling vapor and advection vapor (Fig. 1). At present, warming tinuously by 4.8 cm/10 a during 1961–2001, while the average depth of the climate system is significant, and global annual mean tempera- decreased from 144 cm in 1961–1970 to 124 cm in 1990–2001 (Wang ture has increased by 0.85 °C in the last 100 years (1880–2012) (IPCC, et al., 2005; Li et al., 2019a). In the Tibet autonomous region, the average 2013). Almost all glaciers worldwide have continued to shrink, as re- maximum freezing depth measured at 17 stations also decreased with a vealed by time series of measured changes in glacier length, area, vol- rate of 5.5 cm/10 a during 1961–2010. The rate of decrease increased ume, and mass, and the total mass loss from all glaciers in the world, after 1990; the freezing depth decreased by 14 cm from 1961–1990 to excluding those on the periphery of ice sheets, was very likely 226 ± 1991–2010, while the start date of thawing advanced with a rate of 135 Gt yr−1 in the period 1971–2009 (IPCC, 2013). Satellite records in- 2.1–5.2 d/10 a during 1971–2010 (Du et al., 2012; Li et al., 2019a). dicate that annual mean snow cover extent also decreased with statisti- In the Qilian Mountains, many studies have also confirmed the sig- cal significance over the period 1967–2012 (Bulygina et al., 2009). nificant warming based on records of tree rings and metrological sta- Permafrost temperatures have increased in most regions since the tions (Chen et al., 2012; Xu et al., 2014; Wang et al., 2018), and early 1980s, although the rate of increase has varied regionally, and ac- precipitation increase has also been demonstrated, especially during re- tive layer thicknesses have increased by a few centimeters to tens of cent decades. Under climate warming, the area of 244 glaciers in the centimeters in many areas since the 1990s (Callaghan et al., 2011). eastern Qilian Mountains had decreased by 24.286 km2 in 2007 com- Annual mean temperature also increased by 0.9–1.5 °C in China in pared to the area in 1972, accounting for 23.57% of the glacierized the last 100 years (Ding and Wang, 2016), and temperature increased area in 1972, and 27 glaciers had disappeared by 2007 (Cao et al., by about 1.80 °C during 1960–2007 in the cold regions of western 2010). In the middle Qilian Mountains, glacier area shrank significantly China (Ding and Wang, 2016), where the major cryosphere in China, in- by a total of 138.9 km2, accounting for 35.6% of the glacier area in 1960 cluding all glaciers and most of the permafrost and stable snow cover, is (Bie et al., 2013). In the western Qilian Mountains, the glacier area and distributed (Chen et al., 2018). Under this change, multiphase water ice volume decreased by 17.21% and 24.1% from 1957/1966 to 2010, re- transformation is becoming progressively more accelerative (Kääb spectively (Yu et al., 2014). Additionally, the average decrease of glacier et al., 2007; Kabel et al., 2012; Malatinszky et al., 2013), which is charac- thickness in the Qilian Mountains from 2000 to 2010 was 5.68 ± 2.76 m, terized by the rapidly shrinking cryosphere. In western China, glacier the average glacier mass balance was −0.48 ± 0.23 m w.e·a−1, and the area decreased by 18% from 1970 to 2010, and 5797 glaciers have disap- change of glacier volume was −1.59 ± 0.72 Gt (Gao et al., 2018). Be- peared according to the Second Chinese Glaciers Inventory (Liu et al., tween 1957 and 2007, the Laohugou No. 12 glacier in the western Qilian 2015). Glacier thickness also decreased by 10.56 m between 1980 and Mountains experienced significant thinning and areal shrinkage in the 2005 (China Meteorological Administration, 2006). Ren et al. (2011) ablation zone, the elevation decreased by 18.6 ± 5.4 m, and the total confirmed that the average yearly meltwater runoff from western volume loss for the entire glacier was estimated to be 0.218 km3 China increased from 51.8 × 109 m3 in the 1960s to 79.5 × 109 m3 be- (Zhang et al., 2012). Based on the altitude-response model, the areas tween 2001 and 2006, which contributed 0.12 mm/a to the global of simulated permafrost distribution in the Qilian Mountains in the mean sea level rise. Permafrost showed widespread degradation, in- 1970s, 1980s, 1990s, and 2000s are 9.75 × 104 km2,9.35×104 km2, cluding increased temperature, deeper active layer depth, and reduced 8.85 × 104 km2, and 7.66 × 104 km2, respectively, showing a decreasing Fig. 1. Sketch map for multiphase water transformation in the Qilian Mountains. Z. Li et al. / Science of the Total Environment 663 (2019) 315–328 317 trend over the past 40 years (W. Zhang et al., 2014; L. Zhang et al., 2014). The eastern branch is the Heihe River and the western branch is the Under climate warming, the combination of increasing evapotranspira- Taolaihe River. The Shulehe River Basin, mainly including the tion and diminishing permafrost area has resulted in smoother and flat- Changmahe River and Danghe River, is the third largest inland river ter hydrographs and a reduction in total river discharge, which confirms basin in China, with a whole catchment area of approximately 14.21 the influences of permafrost and climate change on hydrological pro- ×104 km2. The Shiyanghe River Basin, including seven branches, is cesses in the Qilian Mountains (Zhang et al., 2017). Atmospheric the fourth largest inland river basin, with an area of 4.16 × 104 km2.