Empirical evidence of monsoon influences on Asian Lakes

Abstract

Limited information is available on how the Asian monsoon influences contemporary lake processes, seasonal patterns and interannual variation. Data sets from Nepal (Indian monsoon region) and South Korea (East Asian monsoon region) along with published literature show a wide range in the response of Asian lakes to the seasonal monsoon. Cross-system patterns show nutrients and algal biomass peak in most lakes in response to monsoon inflow, which suggests nonpoint sources dominate external loading. This seasonal increase may be the general phenological model for nutrients and phytoplankton in lakes in monsoon regions. Major ions show dilution by surface runoff during the monsoon and post-monsoon increases. Dilution of nutrients in fertile systems during the monsoon suggests point source inputs dominate peak loads during the non-monsoon period. Peak monsoon runoff can enter the water column of large stratified lakes as a density-dependent interflow at depth in the water column with little direct influence on the mixed layer. In these water bodies nutrients in surface water can be lower during strong monsoon seasons because of sub-surface loading. Short-interval data from individual lakes show the linkage between nutrients and phytoplankton biomass can be uncoupled by physical processes and light limitation, resulting in considerable temporal variation. Collectively these mixed responses limit our ability to generalize patterns or predict conditions in individual lakes during the monsoon.

Keywords :

• Asian monsoon
• reservoirs
• nutrient loading
• seasonal patterns