Large-scale national ecological programs alter land-atmosphere water-energy-carbon exchanges by converting vegetation. Previous studies have primarily employed interpretive or statistical attribution analyses to assess the impacts of ecological programs. To accurately quantify the impacts of ecological programs, we propose a definition for the implementation area of ecological programs and delineate its spatiotemporal extent using the adaptive run theory search technique. Subsequently, we employed the MEP-PML and PML-V2-GPP models to quantify the impacts of three major programs (the Three-North Shelterbelt Forest Program (TN), the Grain for Green Program (GGP), and the Grassland Ecological Restoration Program (GERP)) on gross primary productivity (GPP), evapotranspiration (ET), and ET-driven temperature effects across China's arid and semi-arid regions (ASA) over the period 1990-2023. Our analysis reveals that ecological programs increased the annual GPP by 1.73 & times; 10-degrees Pg C yr-1 and reduced annual ET by 2.36 & times; 109 m3 yr-1 . Among them, GERP was the primary contributor to GPP enhancement (3.30 & times;10-degrees Pg C yr-1), while TN showed the highest GPP increase per unit area (4.11 gC m-2 yr-1). In contrast, GGP resulted in a decline in GPP (-2.30 & times; 10-degrees Pg C yr-1). Regarding ET, GERP had negligible impact, TN led to a net increase in ET (52.50 mm yr-1; 3.12 & times;109 m3 yr-1), and GGP caused a net decrease (-54.09 mm yr-1; -7.58 & times;108 m3 yr-1). In terms of thermal effects, increased ET under TN induced a cooling trend (-0.31 degrees C decade-1), whereas reduced ET under GGP produced a warming trend (0.33 degrees C decade-1). This study advances the understanding of the hydrometeorological impacts of ecological programs by shifting from attribution analyses toward quantitative assessment, and contributes to synergies among carbon sequestration, sustainable water resource management, and climate change mitigation through ecological engineering across countries worldwide.