This　study　presents　an　analytical　solution　for　coupled　water–gas　transport　in　a　landfill　cover　system　considering　four　different　root　architectures　(i.e.,　uniform,　triangular,　exponential　and　parabolic　architectures),　which　can　consider　transient　diffusive-advective　transport　of　gas　under　steady-state　water　distributions　in　different　condition　(e.g.,　rainfall　stage　and　evaporation　stage).　The　proposed　solution　is　verified　against　an　existing　analytical　solution,　validated　against　an　experiment,　and　compared　with　a　numerical　solution.　Using　the　verified　analytical　solution,　simulations　were　conducted　on　the　coupled　water–gas　transport.　The　results　show　that　ignoring　water　transport　can　lead　to　significant　error　in　gas　transport　results　under　various　conditions　(e.g.,　the　methane　flux　is　underestimated　by　45%　due　to　ignoring　water　transport,　when　the　desaturation　coefficient　α　is　0.1　m−1).　The　parametric　study　results　indicate　that　triangular　and　exponential　root　architectures　have　greater　effect　on　water–gas　transport　(e.g.,　pore-water　pressure,　gas　emission　fluxes)　compared　with　the　uniform　and　parabolic　root　architectures;　vegetation　has　a　significant　impact　on　the　water–gas　transport,　especially　in　dry　conditions　(e.g.,　the　gas　emission　flux　through　vegetated　cover　is　about　26.3%　lower　than　that　through　the　bare　cover);　the　rainfall　intensity　and　volumetric　water　content　at　the　bottom　boundary　have　significant　effect　on　water–gas　transport　in　the　cover.　The　proposed　analytical　solution　can　be　used　to　aid　the　design　of　vegetated　soil　cover　system　and　the　verification　of　other　more　complex　models.　©　2022