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1. chinaXiv:202101.00074 [pdf]

Long-term variations in runoff of the Syr Darya River Basin under climate change and human activities

Sanim BISSENBAYEVA; Jilili ABUDUWAILI; Assel SAPAROVA; Toqeer AHMED
Subjects: Geosciences >> Geography

In this study, we analyzed the hydrological and meteorological data from the Syr Darya River Basin during the period of 1930–2015 to investigate variations in river runoff and the impacts of climate change and human activities on river runoff. The Syr Darya River, which is supplied by snow and glacier meltwater upstream, is an important freshwater source for Central Asia, as nearly half of the population is concentrated in this area. River runoff in this arid region is sensitive to climate change and human activities. Therefore, estimation of the climatic and hydrological changes and the quantification of the impacts of climate change and human activities on river runoff are of great concern and important for regional water resources management. The long-term trends of hydrological time series from the selected 11 hydrological stations in the Syr Darya River Basin were examined by non-parametric methods, including the Pettitt change point test and Mann-Kendall trend tests. It was found that 8 out of 11 hydrological stations showed significant downward trends in river runoff. Change of river runoff variations occurred in the year around 1960. Moreover, during the study period (1930–2015), annual mean temperature, annual precipitation, and annual potential evapotranspiration in the river basin increased substantially. We employed hydrological sensitivity method to evaluate the impacts of climate change and human activities on river runoff based on precipitation and potential evapotranspiration. It was estimated that human activities accounted for over 82.6%–98.7% of the reduction in river runoff, mainly owing to water withdrawal for irrigation purpose. The observed variations in river runoff can subsequently lead to adverse ecological consequences from an ecological and regional water resources management perspective.

submitted time 2021-01-22 From cooperative journals:《Journal of Arid Land》 Hits457Downloads255 Comment 0

2. chinaXiv:202101.00076 [pdf]

Investigation of crop evapotranspiration and irrigation water requirement in the lower Amu Darya River Basin, Central Asia

Durdiev KHAYDAR; CHEN Xi; HUANG Yue; Makhmudov ILKHOM; LIU Tie; Ochege FRIDAY; Abdullaev FARKHOD; Gafforov KHUSEN; Omarakunova GULKAIYR
Subjects: Geosciences >> Geography

High water consumption and inefficient irrigation management in the agriculture sector of the middle and lower reaches of the Amu Darya River Basin (ADRB) have significantly influenced the gradual shrinking of the Aral Sea and its ecosystem. In this study, we investigated the crop water consumption in the growing seasons and the irrigation water requirement for different crop types in the lower ADRB during 2004–2017. We applied the FAO Penman–Monteith method to estimate reference evapotranspiration (ET0) based on daily climatic data collected from four meteorological stations. Crop evapotranspiration (ETc) of specific crop types was calculated by the crop coefficient. Then, we analyzed the net irrigation requirement (NIR) based on the effective precipitation with crop water requirements. The results indicated that the lowest monthly ET0 values in the lower ADRB were found in December (18.2 mm) and January (16.0 mm), and the highest monthly ET0 values were found in June and July, with similar values of 211.6 mm. The annual ETc reached to 887.2, 1002.1, and 492.0 mm for cotton, rice, and wheat, respectively. The average regional NIR ranged from 514.9 to 715.0 mm in the 10 Irrigation System Management Organizations (UISs) in the study area, while the total required irrigation volume for the whole region ranged from 4.2×109 to 11.6×109 m3 during 2004–2017. The percentages of NIR in SIW (surface irrigation water) ranged from 46.4% to 65.2% during the study period, with the exceptions of the drought years of 2008 and 2011, in which there was a significantly less runoff in the Amu Darya River. This study provides an overview for local water authorities to achieve optimal regional water allocation in the study area.

submitted time 2021-01-22 From cooperative journals:《Journal of Arid Land》 Hits483Downloads277 Comment 0

3. chinaXiv:201910.00054 [pdf]

Ecological biomass allocation strategies in plant species with different life forms in a cold desert, China

FAN Lianlian; DING Junxiang ; MA Xuexi, ; LI Yaoming
Subjects: Environmental Sciences, Resource Sciences >> Basic Disciplines of Environmental Science and Technology

Biomass allocation patterns among plant species are related to their adaptive ecological strategies. Ephemeral, ephemeroid and annual plant life forms represent three typical growth strategies of plants that grow in autumn and early spring in the cold deserts of China. These plants play an important role in reducing wind velocity in the desert areas. However, despite numerous studies, the strategies of biomass allocation among plant species with these three life forms remain contentious. In this study, we conducted a preliminary quadrat study during 2014–2016 in the southern part of the Gurbantunggut Desert, China, to investigate the allocation patterns of above-ground biomass (AGB) and below-ground biomass (BGB) at the individual level in 17 ephemeral, 3 ephemeroid and 4 annual plant species. Since ephemeral plants can germinate in autumn, we also compared biomass allocation patterns between plants that germinated in autumn 2015 and spring 2016 for 4 common ephemeral species. The healthy mature individual plants of each species were sampled and the AGB, BGB, total biomass (TB), leaf mass ratio (LMR) and root/shoot ratio (R/S) were calculated for 201 sample quadrats in the study area. We also studied the relationships between AGB and BGB of plants with the three different life forms (ephemeral, ephemeroid and annual). The mean AGB values of ephemeral, ephemeroid and annual plants were 0.806, 3.759 and 1.546 g/plant, respectively, and the mean BGB values were 0.106, 4.996 and 0.166 g/plant, respectively. The mean R/S value was significantly higher in ephemeroid plants (1.675) than in ephemeral (0.154) and annual (0.147) plants. The mean LMR was the highest in annual plants, followed by ephemeroid plants and ephemeral plants, reflecting the fact that annual plants allocate more biomass to leaves, associated with their longer life span. Biomass of ephemeral plants that germinated in autumn was significantly higher than those of corresponding plants that germinated in spring in terms of AGB, BGB and TB. However, the R/S value was similar in plants that germinated in autumn and spring. The slope of regression relationship between AGB and BGB differed significantly among the three plant life forms. These results support different biomass allocation hypotheses. Specifically, at the individual level, the AGB and BGB partitioning supports the allometric hypothesis for ephemeroid and annual plants and the isometric hypothesis for ephemeral plants.

submitted time 2019-10-26 From cooperative journals:《Journal of Arid Land》 Hits4390Downloads613 Comment 0

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