Analysis of spatial-temporal variations and driving factors of typical
tail-reach wetlands in the Ili-Balkhash Basin, Central Asia
Abstract
In this study, wetlands in the Ili River Delta (IRD) from 1975 to 2020
were extracted based on Landsat images using the object-oriented method;
changes in the wetland area, wetland landscape pattern, NDVI and NPP
were analyzed; and the contributions of natural and human factors to
wetland evolution were quantified. The results indicated that (1) From
1975 to 2020, the wetland area of the IRD showed an increasing trend,
and changes in the wetland area were mainly found in the middle part of
the delta near the Saryesik Peninsula. (2) The wetland landscape pattern
in the IRD changed markedly from 1975 to 2020. The dominant patches of
the wetland in the middle of the delta continued to expand; the patch
aggregation index (AI) increased, and the patch fragmentation index
(LFI) decreased. (3) From 2000 to 2020, the average annual normalized
difference vegetation index (NDVI) and net primary productivity (NPP) in
the IRD increased, which is consistent with the change in wetland
expansion. (4) Inflow to the delta from the Ili River and the water
level of Balkhash Lake are significantly correlated with the wetland
area, which are the dominant factors driving wetland evolution; and
water evaporation from the Kapchagay Reservoir and irrigation water
diversion on the left bank of the reservoir obviously intensified the
process of lake water level decline and wetland degradation during 1970
to 1985. These results can provide scientific background for making
informed ecological protection decisions in the Ili River Delta under
the impacts of climate change and human activities.