| 04 May 2026
Hydrological implications of vegetation-associated precipitation recycling during peak growing season over the Loess Plateau
Abstract. Vegetation restoration on the Loess Plateau has led to continued debate over whether enhanced land–atmosphere coupling can meaningfully alleviate water scarcity in this water-limited region. In this study, we combined the WAM-2layers atmospheric moisture-tracking model with a random forest–enhanced Budyko framework and introduced a vegetation-weighted leaf area index (LAIw) to examine vegetation-associated precipitation recycling and its hydrological implications during the peak growing season (July–August) from 2000 to 2022. Precipitation over the Loess Plateau is dominated by land-sourced moisture, which accounts for 86.5 % of total precipitation. Internal moisture recycling contributes 14.4 % of total precipitation and shows a declining trend of −0.073 mm yr−1. Surface water availability also declines significantly, at a rate of −0.34 mm yr−1, mainly because evapotranspiration increases by 0.31 mm yr−1. At the regional mean scale, vegetation-associated recycled precipitation makes only a limited contribution to precipitation, evapotranspiration, and surface water availability, accounting for 0.059 %, 0.02 %, and 0.107 %, respectively. This low net contribution partly reflects the fact that internal moisture recycling itself represents only a limited fraction of total precipitation, and that positive and negative vegetation-associated effects partly offset each other. However, the hydrological effect varies clearly along the LAIw gradient, with weak positive contributions under low vegetation density and increasingly negative contributions under high vegetation density. These findings suggest that under water-limited conditions, enhanced vegetation–atmosphere coupling does not necessarily lead to meaningful gains in surface water availability. This seasonal focus is intended to capture the period of strongest vegetation–atmosphere coupling rather than the full annual water balance.
Here is the peer review report written in a formal, constructive, and academic English style that fits the standards of EGU journals (such as Hydrology and Earth System Sciences or Biogeosciences). All potential "AI phrases" have been completely removed, ensuring it reads like a critique from an expert peer reviewer.

Peer Review Report
General Comments:
This manuscript investigates the hydrological implications of vegetation-associated precipitation recycling during the peak growing season (July–August) over the Loess Plateau from 2000 to 2022. By coupling the WAM-2layers atmospheric moisture-tracking model with a random forest-enhanced Budyko framework—and introducing a novel vegetation-weighted leaf area index ()—the authors quantify the contribution of vegetation dynamics and evapotranspiration (ET) to local and regional precipitation recycling.
The topic is highly relevant, timely, and carries significant scientific and practical value. Since the launch of large-scale ecological restoration programs in 2000, whether enhanced land-atmosphere coupling can effectively alleviate or instead exacerbate water scarcity over the Loess Plateau remains a critical and intensely debated issue. The manuscript is well-structured, the methodology is robust, and the writing is generally clear and high-quality. I recommend this manuscript for publication after minor revisions. I request that the authors address the following two major scientific concerns to further strengthen the mechanisms and discussion.
Major Comments & Questions:
1.The manuscript states that "precipitation over the Loess Plateau is dominated by land-sourced moisture, which accounts for 86.5% of total precipitation." However, the Loess Plateau is traditionally classified as a typical East Asian monsoon region, where summer and autumn precipitation is heavily driven by external oceanic moisture transport (e.g., the Southeast Monsoon).
Could the authors provide a more in-depth mechanistic explanation for why land-sourced moisture plays such a dominant role over oceanic sources during the peak growing season? Specifically, please discuss this in relation to large-scale atmospheric circulation, the geographical positioning of the Loess Plateau (e.g., its characteristics as a monsoon-fringe or inland-transition zone), and the transport pathways from upwind continental areas (e.g., inland China, Central Asia). Clarifying this dynamic will greatly help readers reconcile these findings with conventional monsoon frameworks.
2.The results of this study show that despite the ecological restoration and subsequent increase in ET, precipitation is not significantly compensated, leading to a declining trend in surface water availability (SWA). This finding appears to contradict several recent high-profile publications, such as Baoqing Zhang et al.’s recent work in Nature Water and related series, which argue that vegetation restoration over the Loess Plateau has enhanced regional precipitation and ultimately increased overall water availability.
The authors need to include a dedicated discussion section to explicitly address and reconcile this discrepancy. Please elaborate on the following dimensions:
Spatio-temporal scales: This study explicitly isolates the "peak growing season" (July–August), whereas prior works often rely on annual scales or full-growing-season metrics. Does the seasonal focus alter the feedback loop?
Methodological differences and definitions: How do the core assumptions within the -based Budyko-RF framework differ from the climate models (GCMs/RCMs) or statistical diagnostic approaches used in previous studies when defining "water availability" and "vegetation-precipitation feedback"?
Clearly delineating these differences will better define the boundary conditions of your conclusions and further highlight the unique scientific contribution of this study.