Climate-Driven Changes in Lake Water Levels and Aquatic Biodiversity. A Case Study of Ghousabad Lake Near the Indus River, Dera Ghazi Khan, Pakistan

Abstract

Climate change is increasingly altering hydrological regimes and aquatic ecosystems across the Indus Basin. This study examines climate-driven variations in water levels, physico-chemical water quality, and aquatic biodiversity at Ghousabad Lake, a shallow freshwater body adjacent to the Indus River in Dera Ghazi Khan District, Punjab, Pakistan, during 2024–2025. Monthly monitoring of water temperature (WT), dissolved oxygen (DO), pH, total dissolved solids (TDS), total alkalinity (TA), total hardness (TH), electrical conductivity (EC), and free carbon dioxide (CO₂) was conducted alongside measurements of lake water levels and indicators of aquatic biodiversity (fish Shannon diversity and phytoplankton abundance). Results revealed pronounced seasonal patterns: WT ranged from 10.5–31.2 °C (mean 22.7 °C), DO from 5.8–10.5 mg/L (mean 8.36 mg/L), and TDS from 851–1191 mg/L. Strong positive correlations existed between WT and TDS, TA, EC, and CO₂ (r = 0.80–0.86), while DO was negatively correlated with WT (r = –0.55). Lake water levels peaked in July–August (influenced by monsoon and Indus flows) and were lower in 2025 than 2024, consistent with regional warming and altered precipitation. Fish diversity declined during peak summer months when DO was lowest and temperatures highest, while phytoplankton abundance increased. Statistical analyses (Pearson correlation, seasonal ANOVA) confirmed significant climate-linked effects. The findings highlight the vulnerability of small Indus-adjacent lakes to climate stressors and underscore the need for integrated monitoring, habitat protection, and adaptive water management to safeguard aquatic biodiversity and ecosystem services in southern Punjab.