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Rapid river basin urbanization inevitably results in drastic increase of water demand which necessitates the development of new water supply schemes to meet the sectorial water resource requirements. Various proposed water resources schemes will need to be evaluated and assessed and the optimum scheme selected for implementation. To prepare for capital budgeting, river basin managers need a set of comprehensive tools for objective decision-making to plan for the water works based on projected water demand due to population growth and water resources regime changes attributed to climate change. A multi-criteria analysis (MCA) approach has been developed for water resources planning with consideration of global changes to plan suitable schemes at various future years, using a set of technical evaluation tools, which comprise (i) water availability, (ii) system reserve capacity, (iii) climate resilience (iv) undeveloped (remaining) yield capacity and (iv) residual flow with respect to environmental flow. The indicators are based on a water resources index (WRI), defined as the ratio of the actual water resource availability (WRA) to the average water resources capacity (WRC) for a specified duration. The novel approach has been applied to Klang River basin in Malaysia, an example of a highly urbanized basin which is heavily dependent on inter-basin water resources. Water demand projection shows that the existing planned water works are inadequate beyond the medium time-horizon between the next five to ten years. There is thus an urgent need to attain water resource self-sufficiency for long-term sustainability. Proposed schemes are evaluated considering climate change up to year 2100. Analysis shows that Klang River basin can benefit from a coastal reservoir designed to intercept the basin river discharge for water resource development to reduce its dependence on inter-basin transfer from the adjacent Selangor River and Langat River basins which are under accelerated development and urbanization to avoid further water competition. The study is an outcome of the program entitled “National Water Balance System (NAWABS)” implemented by the Department of Irrigation and Drainage, Malaysia for basin-level water resource planning and operation towards drought preparedness.

The Yangtze River Valley (YRV) experienced record-breaking extreme high temperature and weakened rainfall events in August 2022, which resulted in severe disasters and large socioeconomic losses. The importance of the intensification and westward movement of the western Pacific subtropical high (WPSH) with abnormal subsidence has been emphasized in previous studies. However, the source of the abnormal subsidence remains unknown. This study investigates the source of the abnormal subsidence over the YRV and discusses its possible causes by adopting the three-pattern decomposition of the atmospheric circulation (3P-DGAC). Meridional circulation (MC) was the main contributor to the abnormal vertical velocity (114%), while the contribution of zonal circulation (ZC) was negative (–14%). Additionally, the negative rainfall anomaly over the YRV can be explained mainly by the MC. The anomalous MC was characterized as a ‘negative-positive-negative-positive-negative’ quintuple distribution with sinking motion over the YRV. Anomalous MC is closely related to the sea surface temperature anomaly (SSTA) over the three oceans. The negative phase of the Indian Ocean dipole (IOD) and La Niña SSTA leads to an anomalous rising motion of the ZC over the Maritime Continent, favoring the existence of the rising motion of the MC by the coupling effect. The positive phase of the North Atlantic triple (NAT) SSTA results in an anomalous Rossby wave train, which further leads to a sinking motion over the YRV.

This paper examines the changes of El Niño–Southern Oscillation (ENSO) associated winter rainfall relationship in Southeast Asia (SEA) in the historical period (1981–2010) and future period (2071–2100) based on the Coupled Model Intercomparison Project Phase 6 (CMIP6) models simulations. Twenty general circulation models (GCMs) are chosen from the Scenario Model Intercomparison Project (ScenarioMIP) highest emission scenario—Shared Socioeconomic Pathway (SSP) 5‐8.5. This study focuses only on the GCMs that have been able to replicate the consistent associated patterns observed, referred to as "teleconnection‐consistent models" (TCMs). During historical period, ENSO has significant negative association with SEA winter rainfall, particularly over Indochina mainland, Maritime Continent (MC) and northern Borneo. The significant negative‐associated teleconnection affected area has increased under future climate, particularly over southern part of South China Sea (SCS). The weakening of south westerlies at Western North Pacific (WNP) centred near 20°N reduces the moisture transport from Indochina into south of China, increase the negative correlated affected area in the SEA regions above equator. The northeasterlies/easterlies that prevailed from the WNP anticyclone (AC) brings significant moisture flux into southern Borneo, causing increment of significant positive‐associated moisture flux convergence to that region. The weakening of upward motion in TCM results in less warm and moist air rising over SEA MC, reducing the rainfall availability. The 1° eastward expansion of WC downward branch eastern edge leads to suppression of convective activities, increasing the dry affected area. The results suggest that the ENSO has a larger influence on the negative‐associated SEA rainfall and atmospheric circulation in the December–January–February (DJF) late‐21st century when compared to the 1980–2010. [ABSTRACT FROM AUTHOR]