Figure 4

ERA and APH data based linear trends for Mangla-Jhelum basin, Tarbela-Indus basin and overall basin. The ERA based Tp and APH based Ap show a significant decrease of 5.38 mm year⁻¹, 4.68 mm year⁻¹, 8.40 mm year⁻¹ and 319 km² year⁻¹, 310 km² year⁻¹ and 358 km² year⁻¹, respectively. Two very strong El Niño events of 1982–1983 and 1997–1998 reduced Tp (from 481 mm year⁻¹ to 292 mm year⁻¹ and 591 mm year⁻¹ to 446 mm year⁻¹ for 1982–1983 and 1997–1998). A similar decrease in Tp has been observed for Mangla-Jhelum basin during 1982–1983 and 1997–1998 (from 358 mm year⁻¹ to 292 mm year⁻¹ and 438 mm year⁻¹ to 346 mm year⁻¹, respectively). The Ap also decreased from 50233 km² year⁻¹ to 42442 km² year⁻¹ and 48286 km² year⁻¹ to 39758 km² year⁻¹ for Tarbela during 1982–1983, and 1997–1998. Mangla also shows a decrease in Ap during 1982–1983, 1997–1998 and 2007 (44180 km² year⁻¹ to 38432 km² year⁻¹, 40199 km² year⁻¹ to 34740 km² year⁻¹ and 36543 km² year⁻¹ to 30230 km² year⁻¹, respectively). Strength of ENSO phases are represented by VS (very strong), S (strong), M (moderate), W (weak) and N (neutral).