Understanding the effect of long term and short term hydrological components on landscape ecosystem

Abstract

Modifications in river morphology are witnessed due to the hydrological fluctuations leading to braided rivers and sandbar developments. Understanding the hydrological alterations could offer crucial insight into the ecosystem's landscape pattern. To comprehend flood and drought in an agricultural ecosystem, we investigated the impact of short-term water level changes from 1999 to 2015. Numerical simulations were carried out on the fluctuant streamflow at different seasons in a braided river using a two-dimensional hydrodynamic model. The number of consecutive wet days (CWD), average wet days (AWD), consecutive dry days (CDD), and average dry days (ADD) were computed. The Standardized Streamflow Index (SSFI-4) was determined at a seasonal time scale, which is used to quantify the streamflow-based hydrological droughts. The calibration and validation of the hydrodynamic model was done with the measured velocity. To understand the planform geometry of the river, satellite images were derived for the historical period from 1976 to 80 till 2016–17. The Planform Index (PI) and Sinuosity Index (SI) were used to assess and classify the river into straight, braided and meander categories. Speedy modifications were observed across the longitudinal profile, with PFI varying between 3.72 and 42.8. Sandbars being an imperative asset for floodplain communities and dwellers, the effect of these fluctuations was studied in different landscape classes. We analyzed the changes in the spatial and temporal characteristics of dynamic landscape patterns between 2004 and 2014 at quinquennial and decadal scales. We found that a substantial-high water level from a 2010 flood led to a drastic change in the landscape pattern of the ecosystem. In addition, consecutive dry days witnessed over the sandbar regions affect the agriculture cropping patterns. Post flooding, the expansion of land under agriculture could be inferred from the fact that sediment was fertile and deposited after the flood recession; agriculture was dominantly practiced in the region. Overall, the study demonstrated that various hydrological components typically impact the spatial distribution characteristics of landscape patterns.