Abstract <p>The study of changes in vegetation and water availability is significant for managing land, especially in Bihar, which often faces changing weather. However, earlier studies lacked an in-depth assessment of the variability and interdependency of these two factors. This study fills that gap by assessing the vegetation and water dynamics, as well as their interdependency, over time. Key spectral indices, Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI), were employed to evaluate vegetation cover and water distribution. The results show a small rise in vegetation (NDVI) with an increase of 0.0044, and a slow drop in water (NDWI) with a decrease of –0.0133. Further, from 2021 to 2024, Bihar’s NDVI ranged from a mean of 0.3751 to 0.4294, with consistently high kurtosis (&gt;5), indicating stable vegetation cover with occasional dense patches. In contrast, NDWI had negative mean values (–0.3709 to –0.4591) and high skewness (up to 2.40) and kurtosis (up to 13.75), reflecting predominantly dry conditions with sporadic water presence. NDVI only showed a significant decline in June (Sen’s slope = –0.01883, <i>p</i> = 0.0415), while NDWI showed moderate but non-significant decreases in March (–0.04132), December (–0.02625), and September (–0.01349). The data also show that both NDVI and NDWI have stayed mostly steady over the years, and there is a strong opposite link between the amount of vegetation and the amount of surface water. A very strong negative correlation (<i>r</i> = –0.9749) was found between average NDVI and NDWI. Also, percentage change showed large changes in both, with NDVI going up by 15.26% from 2021 to 2022, and NDWI going down sharply by 24.57% in 2022. NDVI showed a CV of 21–23%, indicating high variability in vegetation cover, while NDWI recorded a CV of 17–18%, reflecting noticeable fluctuations in water availability. However, no unusual values were found in the trend. This study can help in making better decisions for effective land and water management. It can also help in making policies for protecting the environment and improving farming.</p> Research highlights <p><OrderedList> <ListItem> <ItemNumber>1.</ItemNumber> <ItemContent> <p>Steady vegetation and declining water trends</p> </ItemContent> </ListItem> <ListItem> <ItemNumber>2.</ItemNumber> <ItemContent> <p>Strong inverse NDVI–NDWI relationship observed</p> </ItemContent> </ListItem> <ListItem> <ItemNumber>3.</ItemNumber> <ItemContent> <p>June shows significant NDVI decline</p> </ItemContent> </ListItem> <ListItem> <ItemNumber>4.</ItemNumber> <ItemContent> <p>High kurtosis indicates dense vegetation patches</p> </ItemContent> </ListItem> <ListItem> <ItemNumber>5.</ItemNumber> <ItemContent> <p>Notable interannual variability in both indices</p> </ItemContent> </ListItem> </OrderedList></p>