Glacier Runoff Variation Since 1981 in the Upper Naryn River Catchments, Central Tien Shan

Water resources in Central Asia strongly depend on glaciers, which in turn adjust their size in response to climate variations. We investigate glacier runoff in the period 1981–2019 in the upper Naryn basin, Kyrgyzstan. The basins contain more than 1,000 glaciers, which cover a total area of 776 km2. We model the mass balance and runoff contribution of all glaciers with a simplified energy balance melt model and distributed accumulation model driven by ERA5 LAND re-analysis data for the time period of 1981–2019. The results are evaluated against discharge records, satellite-derived snow cover, stake readings from individual glaciers, and geodetic mass balances. Modelled glacier volume decreased by approximately 6.7 km3 or 14%, and the majority of the mass loss took place from 1996 until 2019. The decreasing trend is the result of increasingly negative summer mass balances whereas winter mass balances show no substantial trend. Analysis of the discharge data suggests an increasing runoff for the past two decades, which is, however only partly reflected in an increase of glacier melt. Moreover, the strongest increase in discharge is observed in winter, suggesting either a prolonged melting period and/or increased groundwater discharge. The average runoff from the glacierized areas in summer months (June to August) constitutes approximately 23% of the total contributions to the basin’s runoff. The results highlight the strong regional variability in glacier-climate interactions in Central Asia.

Analysis of Runoff Variation Characteristics and Influencing Factors in the Wujiang River Basin in the Past 30 Years

Changes in climate and the underlying surface are the main factors affecting runoff. Quantitative assessment of runoff characteristics, and determination of the climate and underlying surface contribution to changes in runoff are critical to water resources management and protection. Based on the runoff data from the Wulong Hydrological Station, combined with the Mann-Kendall test, Indicators of Hydrologic Alteration (IHA), Budyko hypothesis, and changes in climate and the underlying surface, this study comprehensively analyzed the runoff in the Wujiang River Basin (WRB). The results showed that: (1) The annual runoff of Wujiang River showed a downward trend, and an abrupt change occurred in 2005. (2) The overall hydrological change in WRB is 46%, reaching a moderate change. (3) The contribution rates of precipitation (P), potential evaporation (ET0), and underlying surface to runoff changes are 61.5%, 11.4%, and 26.9%, respectively. (4) After 2005, the WRB has become more arid, human activities have become more active, vegetation coverage has increased, and the built-up land has increased significantly.

Identifying the runoff variation in the Naryn River Basin under multiple climate and land-use change scenarios

A multiple scenario-based ensemble prediction (MSEP) method is developed for exploring the impacts of climate and land-use changes on runoff in the Naryn River Basin. MSEP incorporates multiple global climate models, Cellular Automata–Markov and Soil and Water Assessment Tool (SWAT) within a general framework. MSEP can simultaneously analyze the effects of climate and land-use changes on runoff, as well as provide multiple climate and land-use scenarios to reflect the associated uncertainties in runoff simulation and prediction. Totally 96 scenarios are considered to analyze the trend and range of future runoff. Ensemble prediction results reveal that (i) climate change plays a leading role in runoff variation; (ii) compared to the baseline values, peak flow would increase 36.6% and low flow would reduce 36.8% by the 2080s, which would result in flooding and drought risks in the future and (iii) every additional hectare of arable land would increase the water deficit by an average of 10.9 × 103 m3, implying that the arable land should be carefully expanded in the future. Results suggest that, to mitigate the impact of climate change, the rational control of arable land and the active promotion of irrigation efficiency are beneficial for water resources management and ecological environmental recovery.

Study on the Impact of Land-Use Change on Runoff Variation Trend in Luojiang River Basin, China

To reveal the influence process of land use changes on runoff variation trends, this paper takes the Luojiang River of China as the study area, and the Soil and Water Assessment Tool (SWAT) model was constructed to quantitatively analyze the impact of different land uses on runoff formation in the watershed, and used the Cellular Automata-Markov (CA-Markov) model to predict future land use scenarios and runoff change trends. The results show that: (1) the SWAT model can simulate the runoff in the Luojiang River basin; (2) the runoff in the Luojiang River basin has a decreasing trend in recent 10 years, caused by the decrease of rainfall and runoff due to changes in land use; (3) the forecast shows that the land-use changes in the basin will lead to an increase in runoff coefficient in 2025. The increase of the runoff coefficient will bring some adverse effects, and relevant measures should be taken to increase the water storage capacity of urban areas. This study can help plan future management strategies for the study area land coverage and put forward a preventive plan for the possible adverse situation of runoff variation.

Attribution Analysis of Runoff Variation in Kuye River Basin Based on Three Budyko Methods

The Loess Plateau is the main soil erosion area within the Yellow River Basin. Quantifying the contribution rate of climate change and human activities to runoff change can provide support for water resources management in the Yellow River Basin. Kuye River Basin is located in the Loess Plateau. As a first-class tributary of the Yellow River, it was selected as the study area. Runoff from the Kuye River Basin has decreased significantly since the 1990s owing to climate change and anthropogenic coal mining. The main objective of this study was to quantify the contribution and sensitivity of climate change and anthropogenic activities to runoff changes using three popular Budyko and elasticity coefficient methods, as well as to compare the similarities and differences among the three methods. The results show that: (1) Through four mutation point test methods, the change point of runoff in the study period of Kuye River Basin is 1997. (2) The elasticity coefficients calculated by the three Budyko methods showed that during the study period, the runoff was more sensitive to changes in precipitation, followed by the catchment surface characteristic parameters and the potential evapotranspiration. (3) All three Budyko methods can yield reasonable contributions of climate change and human activity to runoff changes. The three methods together indicate that the influence of the catchment surface characteristic parameters is the most important factor for the runoff variation in the Kuye River.

The Spatiotemporal Regime of Glacier Runoff in Oases Indicates the Potential Climatic Risk in Dryland Areas of China

Glaciers continuously affected by climate change are of great concern; their supply and runoff variation tendency under the pressure of increasing populations, especially in dryland areas, should be studied. Due to the difficulty of observing glacier runoff, little attention has been given to establishing high-resolution and long-term series datasets established for glacial runoff. Using the latest dataset using digital elevation models (DEMs) to obtain regional individual glacier mass balance, simulating the spatiotemporal regime of glacier runoff in oases that support almost the entire income in the dryland areas of China (DAC) could be possible. The simulations quantitatively assess glacier runoff, including meltwater runoff and delayed runoff, in each basin of the DAC at a spatial resolution of 100 m from 1961 to 2015, classify glaciers according to the potential climatic risks based on the prediction results. The total glacier runoff in the DAC is (98.52 ± 67.37) × 108 m3, in which the meltwater runoff is (63.43 ± 42.17) × 108 m3, accounting for 64.38 %. Most basins had continuously increasing tendencies of different magnitudes from 1961 to 2015, except for the Shiyang River basin, which reached its peak in approximately 2000. Glacier runoff nurtured nearly 143,939.24 km2 of oasis agricultural areas (OAA) until 2015, while 19 regions with a total population of 14 million were built alongside the oases, where glacier runoff occupies an important place in agricultural, industrial and municipal water consumption. Therefore, providing a long time series of glacier runoff for different river basins is of great significance to the sustainable development of the oasis economy in the arid zones.

A comprehensive runoff variation evaluation system of the Yarlung Zangbo River based on vague sets

Runoff processes are the basis for maintaining the safety of river ecosystems. The Yarlung Zangbo River (YZR) faces changes in flow regimes due to the impacts of human activities and climate change#which may threaten its fragile ecosystem. In this study#a new comprehensive system for evaluating runoff variation was constructed to investigate the degree of runoff alternation in the YZR. Based on the data from the primary hydrological stations in the YZR from 1956 to 2000#the assessment indicators of runoff variation were selected by considering the flow#sediment#and water temperature processes. Furthermore#a comprehensive evaluation system for runoff variation was constructed via multiple hydrological analysis methods and vague sets. The results showed that the variation index of the YZR from 2010 to 2013 was 0.15–0.20 compared with the flow regimes of the YZR before 2000#which were within a reasonable range#indicating that the comprehensive runoff conditions of the YZR were not greatly disturbed by human activities such as reservoir construction and river regulation during this period. These results provide a tool for evaluating the runoff change in the YZR and new references for researching runoff variation in other similar watersheds.