Modelling the relationship between groundwater depth and NDVI using time series regression with Distributed Lag M

Margaret Phiri,Solomon G Tesfamichael,Yegnanew A Shiferaw

doi:10.4314/sajg.v7i2.4

Abstract

Groundwater plays a key role in hydrological processes, including in determining aboveground vegetal growth characteristics and species distribution. This study aimed at estimating time-series data of Normalized Difference Vegetation Index (NDVI) using groundwater depth as a predictor in two land cover types: grassland and shrubland. The study also investigated the significance of past (lagged) groundwater and NDVI in estimating the current NDVI. Results showed that lagged groundwater depth and vegetation conditions influence the amount of current NDVI. It was also observed that first lags of groundwater depth and NDVI were significant predictors of NDVI in grassland. In addition, first and second lags of NDVI were consistently significant predictors of NDVI in shrubland. This shows the importance of vegetation type when modelling the relationship between groundwater depth and NDVI.Keywords: Groundwater depth; Landsat NDVI; Time-series analysis; Distributed Lag Models

Highlights

Groundwater plays an important role in the growth of aboveground vegetation (Fan et al, 2016; Rodriguez et al, 2016; Werner et al, 2017)
The analysis showed that groundwater depth had a major influence on Normalized Difference Vegetation Index (NDVI) values, with areas having shallower groundwater depth corresponding to higher NDVI values
The model fit statistics including R-squared, the significance level of Fstatistic (p values), Akaike information criteria (AIC), Bayesian information criteria (BIC), log-likelihood and Mean absolute scaled error (MASE) MASE confirmed the superiority of ARD models

Summary

Introduction

Groundwater plays an important role in the growth of aboveground vegetation (Fan et al, 2016; Rodriguez et al, 2016; Werner et al, 2017). This is the case in arid areas where rainfall and surface water levels are low or unpredictable (Wada et al, 2010; Jin et al, 2011; Orellana et al, 2012; Liu et al, 2013). Ghose et al (2018) showed the importance of evapotranspiration and runoff in influencing groundwater level in an arid environment Another important factor that complicates the relationship between groundwater and vegetation amount is land use type. Huang et al (2018) observed that older orchard farms depleted groundwater more than younger orchards and farmlands

Objectives

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Conclusion