The contribution of permafrost and snow to the water balance under climate change conditions (Aksu catchment, Central Tian Shan, P.R. China)
- Research Project supported by Deutsche Forschungsgemeinschaft, Bonn (KI261/22-1)
- Short term: “AKSU TARIM-CRYO”
- Project funding: March 2010 to February 2013
Upper Xiqiong Tailan Glacier and crest of Tomur Mountain (7435 m).
Photo: Liu Shiyin, 2008
Project Summary and Research Aims
The Aksu-Tarim catchment in western China is a quickly developing region with increasing water demand. Given its extraordinary topographic heterogeneity with high-mountain ridges and large desert basins, the assessment of the hydrological cycle is a scientific challenge because it includes, in particular, the cryosphere in the form of glaciers, snow cover and permafrost. Furthermore, the estimate of future freshwater availability in the light of climate change is a key issue for agricultural planning, food security and urbanization in western China. Compared with the eastern Tian Shan region, including the “Tian Shan Glacier Number One” in the Urumqi He catchment, our study area has barely been focused by integrative research activities.
It is well known, that climate warming actually leads to an accelerated ablation and retreat of high mountain glaciers in most parts of the world, and to a runoff increase in the short to middle term. However, the contribution of water reservoirs from the periglacial belt to runoff formation is almost unknown, although it becomes increasingly important in rather arid mountain areas. This applies certainly for the Central Tian Shan, delivering water to the Taklamakan, a quickly developing region in an extremely arid environment with permanent water shortage.
Main scientific tasks in this interdisciplinary project therefore include
- an improvement of knowledge on permafrost distribution, and concerned periglacial processes and hazards,
- the investigation of relevant hydrologic parameters in unglaciated, periglacial environments (ice content, active layer thickness), and
- the investigation of the relevant hydrological parameters of the perennial snow cover (areal distribution, thickness, water equivalent).
The AKSU-CRYO-Project will supply these results through detailed field studies at field sites selected in coordination with Chinese scientists and their current projects. In a second step, modelling of the cryosphere by using input parameters from the CLIM-subproject and of exemplary data on perennial snow fields from the RS-subproject will allow assessing the relevance of hydrologic components of the cryosphere to the overall hydrological cycle in the region.
The main research aims can be summarized as follows:
- Understanding the variability of ground thermal and moisture regimes under the periglacial conditions of the investigated catchment areas on a local to regional scale,
- Understanding the distribution patterns and characteristics of seasonally and perennially frozen ground, and of perennial snow fields. Assessing the relevance of these components to the hydrological cycle on a local to regional scale in view of changing climate conditions,
- Developing models for frozen ground distribution and characteristics with their effects on the hydrological cycle, for estimating the present ground ice volume, and the additional ice volume available for the water budget under warming climate conditions.
- Understanding the active layer processes and their effects on geomorphologic activity and hazards, also in view of changing climate conditions,
- Contributing basic data to geomorphologic and ecological working groups on the Chinese side, and continuing data exchange with Chinese partner institutions,
In addition to the modelling products listed above, the final results will consist of
- a digital permafrost and geomorphologic map at a scale of 1:50.000 for the Keqikar and Gukur research areas containing ground temperatures, active layer thicknesses, and observations of ground-ice as point observations,
- a modelled permafrost map at a scale of 1:100.000 for the Central Tian Shan with calculated ground temperatures, active layer thicknesses, and climate information. Ground-ice observations and estimates will be included, wherever possible.
Main research areas are:
- Area for intensive local climatological and geomorphological field studies
- (periglacial areas of the catchments Gukur and Keqikar).
- Area for permafrost modelling (Central Tian Shan from bordering mountain crests to river mouths of Keqikar, Gukur, Tomur and Xiqiong Tailan into Kumarik River). Permafrost modelling will be based on the meteorological data and permafrost related ground information obtained by field studies at Gukur and Keqikar glaciers.
- Regional area with good information concerning climate and hydrology exist. It covers the whole catchments of the Aksu and Koksal rivers, including areas in Kirgistan.
There is a strong climatological gradient from the East to the Central Tian Shan.
Glaciers in the Central Tian Shan research area with the catchments of the rivers Keqikar, Tailan, Gukur and Tomur (cp. latitude coordinates for scale)
Cooperation with German Partner Projects
The research project AKSU TARIM-CRYO is part of the AKSU TARIM PROJECT GROUP
„Climate Change and Water Resources in Western China“. The main goal of this research group is the integrative assessment of the local to regional hydrological cycle including the atmospheric components, the processes related to glaciers, snow cover and permafrost as well as the river runoff at the southern slopes of the Tian Shan mountains. Scientists from several German universities have joined together with scientists from reputable Chinese research institutes and universities in order to tackle the quantification of the hydrological cycle and the future perspective of freshwater availability in western China, particularly in the Aksu Tarim basin. The following work will be done:
- The atmospheric component of the hydrological cycle and the issue of anthropogenic climate change will be addressed by a chain of global, regional and local climate models and validated with post-processed observational data in the AKSU TARIM-CLIM project (universities of Würzburg and Hamburg).
- Field and modelling studies at the scale of individual glaciers will be dealt with in the AKSU TARIM-MELT project (University of Munich). The aim is to improve our knowledge of ablation as a function of surface structures on glaciers with and without debris cover by an extended ablation model. In addition, the resulting runoff as a crucial contribution to total freshwater availability in the Aksu Tarim basin will be assessed by a hydrological model.
- Perennial snow fields and permafrost in various parts of the Tian Shan mountains will be examined by the University of Giessen in the AKSU TARIM-CRYO project. Detailed field studies with respect to permafrost and active layer distribution, characteristics and dynamics, and additionally perennial snow fields as permafrost indicators are dedicated to assess the relevance of these components of the cryosphere to the overall hydrological cycle in the region.
- While AKSU TARIM-MELT and AKSU TARIM-CRYO are focused on the local scale of individual glaciers and valleys, the regional perspective of the cryosphere is addressed in the AKSU TARIM-RS project (University of Dresden). Based on remote sensing data the variability and changes of the glacier extent in the entire Aksu Tarim catchment are studied.
All these research activities are tackled together by German and Chinese scientists. The Chinese scientists provide essential knowledge on the local and regional characteristics of the study area and are involved in various Chinese research programmes dedicated to the climatologic, glaciological and hydrological assessment of western China. The cooperation will include the exchange of knowledge and methods, the joint analysis of data and the joint publication of the results.
Chinese and Central Asian Partner Projects (CAREERI, LUCA)
Main Chinese partners are scientific research groups of the world-renowned research centre CAREERI in Lanzhou, China (Cold and Arid Regions Environmental and Engineering Research Institute). The Chinese contribution is intended by the following working groups: On-site measurements on Qingbingtan glacier in Gukur River (Prof. LI Zhongqin), climate change’s impact on water resources (Prof. SHEN Yongping) and hydrological modelling (Dr. XI Haiyang).
The economic development of northwest China (Taklamakan basin) depends to a considerable extent on the melt-water originating in the upper Aksu Tarim river system with ice- and snow-covered areas located in Kirgistan. A strong German-Chinese-Kirgiz cooperation is therefore essential. Within the project “Land Use, Ecosystem Services and Human Welfare in Central Asia” (LUCA) a comparable research approach has been chosen in order to develop scenarios for neighbouring rivers in Kirgistan. The LUCA subproject SP1 “Water Resources of Central Asian Mountain Areas – relevance for the agriculture in semiarid regions under climate change conditions” is coordinated by Prof. King (research centre ZEU of Giessen university) and Prof. Usubaliev (CAIAG Bishkek).