The Potential To Reconstruct Manasi River Streamflow In The Northern Tien Shan Mountains (NW China) Item Type Article; text Authors Yuan, Yujiang; Shao, Xuemei; Wei, Wenshou; Yu, Shulong; Gong, Yuan; Trouet, Valerie Citation Yuan, Y., Shao, X., Wei, W., Yu, S., Gong, Y., Trouet, V., 2007. The potential to reconstruct Manasi River streamflow in the northern Tien Shan Mountains (NW China). Tree-Ring Research 63(2):81-93. Publisher Tree-Ring Society Journal Tree-Ring Research Rights Copyright © Tree-Ring Society. All rights reserved. Download date 02/10/2021 16:33:22 Link to Item http://hdl.handle.net/10150/622559 TREE-RING RESEARCH, Vol. 63(2), 2007, pp. 81–93 THE POTENTIAL TO RECONSTRUCT MANASI RIVER STREAMFLOW IN THE NORTHERN TIEN SHAN MOUNTAINS (NW CHINA) YUJIANG YUAN* Institute of Desert Meteorology CMA, Urumqi 830002, China Swiss Federal Research Institute WSL 8903 Birmensdorf, Switzerland XUEMEI SHAO Institute of Geographical Sciences and Resources CAS, Beijing 100101, China WENSHOU WEI and SHULONG YU Institute of Desert Meteorology CMA, Urumqi 830002, China YUAN GONG Hydrological and Water Resources Bureau of Xinjiang Urumqi 830000, China and VALERIE TROUET Swiss Federal Research Institute WSL 8903 Birmensdorf, Switzerland ABSTRACT We present a tree-ring based reconstruction of water-year (October–September) streamflow for the Manasi River in the northern Tien Shan mountains in northwestern China. We developed eight Tien Shan spruce (Picea schrenkiana Fisch. et Mey.) chronologies for this purpose, which showed a common climatic signal. The hydroclimatic forcing driving tree growth variability affected streamflow with a three- to four-year lag. The model used to estimate streamflow is based on the average of three chronologies and reflects the autoregressive structure of the streamflow time series. The model explains 51% of variance in the instrumental data and allowed us to reconstruct streamflow for the period 1629–2000. This preliminary reconstruction could serve as a basis for providing a longer context for evaluating the recent (1995–2000) increasing trends in Manasi River streamflow and enables the detection of sustained periods of drought and flood, which are particularly challenging for managing water systems. Several of the reconstructed extended dry (wet) periods of the Manasi River correspond to reconstructed periods of drought (flood) in Central Asia in general and in other Tien Shan mountain locations in particular, suggesting that the analysis of Tien Shan spruce could contribute significantly to the development of regionally explicit streamflow reconstructions. * Corresponding author: [email protected] Copyright ’ 2007 by The Tree-Ring Society 81 82 YUAN, SHAO, WEI, YU, GONG, and TROUET Keywords: tree-ring chronology, streamflow reconstruction, Picea schrenkiana, Tien Shan Mountains, Manasi River, northwestern China. INTRODUCTION mountain range), but a decreasing streamflow in rivers at lower elevations. Enhanced annual The Tien Shan in northwestern China has streamflow has been detected in glacier-fed rivers, experienced dramatic climatic and hydrologic where the proportion of glacier melt water has changes since the beginning of the 20th Century increased over recent decades (Ye et al. 1999; Xie in general and in the last few decades in particular. et al. 2004). Despite the explicit interannual trend Human-induced global CO enrichment has led to 2 in glacier-fed river streamflow, the persistence of unambiguous warming over central Asia (Hansen seasonal streamflow distribution is unreliable (Xie 1988; Esper et al. 2002; Hu et al. 2003; Tian et al. et al. 2004). Streamflow of many rivers in the 2006). The northern Tien Shan mountain range in Xinjiang autonomous province has increased in particular has been characterized by increasing th Spring since the 1980s, coinciding with intensive temperatures over the second half of the 20 snowmelt, but decreased in Summer (Ye et al. Century (Aizen et al. 1997; Esper et al. 2003; Su et 1999). The poor reliability of surface water al. 2005; Ye et al. 2005; Esper et al. 2007). Glacier resources is an impediment for their utilization retreat and glacier melt in the Tien Shan moun- and sustainable management. Climate modeling tains were enhanced by temperature increases (Xie efforts (Gao et al. 2001) predict a further increase et al. 2004; Su et al. 2005; Ye et al. 2005). in precipitation and annual streamflow under Rising temperatures since the 1980s were potentially steeper CO2 enrichment conditions in accompanied by an increasing trend in precipita- the near future. tion (Aizen et al. 1997, 2001; Su et al. 2005; Ye et The observed increasing trends in tempera- al. 2005; Shi et al. 2007), leading to an increase in ture, precipitation, and streamflow since the 1980s flood frequency and flooded area (Jiang et al. indicate that a climate shift from warm-dry to 2005; Mao et al. 2005). Although social factors warm-wet has occurred in northwestern China (e.g. land use change) have been proposed as (Shi et al. 2007). The temporal (decadal or drivers of flood disaster increases (Jiang et al. centennial scale) and spatial extent of this climate 2002), recent floodings have generally been attrib- shift, however, is subject to important uncertain- uted to natural factors and global warming. Like ties. An extensive hydrometeorological network many developing countries, China is strongly has been established in the Tien Shan area, but affected by natural hazards and extreme climatic reliable instrumental data are only available from events, floods in particular. Flood disasters the 1950s onwards (Aizen et al. 1997). Quantita- threaten agricultural development, property, and tive information about long-term hydroclimatic human lives, and the associated economic losses variability therefore needs to be recovered from hinder regional economic development (Jiang et proxy records to view recent climatic change in al. 2005). a longer-term perspective. Tree-ring data are Annual streamflow of rivers in the Tien Shan particularly valuable in this context, because of area has generally increased since the 1980s, their strong climatological sensitivity, their exten- because of increased precipitation and enhanced sive spatial distribution, and the possibility for glacier melt (Mao et al. 2004; Chen et al. 2005; Ye precise, absolute dating (Fritts 1976). et al. 2005; Shi et al. 2007). The response of Tree-ring analysis has been successfully ap- streamflow to climate variability, however, is plied to reconstruct drought variability in central regionally variable (He et al. 2003; Shi et al. Asia (Pederson et al. 2001; Wang et al. 2005; Davi 2007). Gong et al. (2003) found an increase in et al. 2006; Li et al. 2006; Treydte et al. 2006). streamflow in rivers with runoff-producing areas Tree-ring based streamflow reconstructions have at high elevations (e.g. northern Tien Shan been developed for many areas (e.g. Schulman Tien Shan Streamflow Reconstruction 83 1945; Cook and Jacoby 1983; Cleaveland and ized by steep slopes, shallow soil substrates, and Stahle 1989; Cleaveland 2000; Case and McDon- little anthropogenic disturbance. Between 39 and ald 2003; Gedalof et al. 2004; Woodhouse and 62 samples were collected per site (Table 2). Lukas 2006), but few streamflow reconstructions All cores were air-dried, mounted, and are available for central Asia (Pederson et al. sanded with increasingly fine grade sandpaper to 2001) and the Tien Shan range (Li and Yuan 1996; highlight tree-ring borders (Stokes and Smiley Li et al. 1994, 1997; Yuan et al. 1996, 2001). 1996). Ring widths were measured to the nearest The Manasi River has the largest streamflow 0.001 mm using a VELMEX measuring system, among rivers on the northern slope of the Tien and standard dendrochronological techniques Shan mountain range in northwestern China and applied for crossdating and chronology develop- is the major water resource for the Manasi oasis in ment (Fritts 1976; Cook and Kairiukstis 1990). Xinjiang. This study aims at reconstructing de- The quality of measurements and visual cross- cadal- to centennial-scale streamflow variability dating was examined using COFECHA software for the Manasi River. For this purpose, we (Holmes 1983) and crossdated series were stan- collected Tien Shan spruce tree-ring samples at dardized using ARSTAN software (Holmes 1992). eight sites in the mountains surrounding the Standardization was applied to remove age and Manasi River basin. other non-climatic trends and involved fitting a spline that was two thirds the length of the MATERIAL AND METHODS common period of the tree-ring series. The Expressed Population Signal (EPS; Wigley et al. Study Area 1984) was used to assess the loss of common The Manasi River headwaters are located on variance over time with decreasing sample size for the Yilianhabierga Mountain on the north slope of all chronologies. The chronologies were truncated the Tien Shan mountain range. After collecting 10 when EPS dropped below 0.85. tributaries such as the Qingshui River, the Manasi We used the eight standardized tree-ring River flows out of the valley and crosses the chronologies to model water-year streamflow. pediment at the Kensiwate hydrological station Standardized chronologies are more appropriate (Fig. 1). The catchment of the Manasi Basin up to for open-canopy sites (such as our study sites) the Kensiwate hydrological station is 5211 km2. than prewhitened chronologies (Cook 1985). Elevations in the watershed range from 940 to 5289 m. Thirty-eight percent of the basin is Hydrometeorological Data situated at elevations above 3600 m, which are perennially snow-covered. The runoff-source area We employed water-year (October–Septem- below the snow line, at elevations of 1500 to ber) streamflow data from the Manasi River, 3600 m, is well vegetated and has ample pre- gauged at the Kensiwate hydrological station, for cipitation. Tien Shan spruce forests form an tree-ring calibration. These data were provided by important zonal vegetation type in Northwest the Hydrological and Water Resources Bureau of China (Wang et al. 2004) and are distributed Xinjiang. As no time series of monthly streamflow between 1800–2600 m in the Manasi River Basin.