Establishing ecological thresholds and targets for groundwater management

Groundwater is critical for many ecosystems, yet groundwater requirements for dependent ecosystems are rarely accounted for during water and conservation planning. Here we compile 38 years of Landsat-derived normalized difference vegetation index (NDVI) to evaluate groundwater-dependent vegetation responses to changes in depth to groundwater (DTG) across California. To maximize applicability, we standardized raw NDVI and DTG values using Z scores to identify groundwater thresholds, groundwater targets and map potential drought refugia across a diversity of biomes and local conditions. Groundwater thresholds were analysed for vegetation impacts where ZNDVI dropped below −1. ZDTG thresholds and targets were then evaluated with respect to groundwater-dependent vegetation in different condition classes and rooting depths. ZNDVI scores were applied statewide to identify potential drought refugia supported by groundwater. Our approach provides a simple and robust methodology for water and conservation practitioners to support ecosystem water needs so biodiversity and sustainable water-management goals can be achieved.

地下水对许多生态系统至关重要，但在水资源和保护规划过程中，依赖地下水的生态系统对地下水的需求却很少被考虑在内。在此，我们收集了38年由陆地卫星得出的归一化植被指数（NDVI），以评估加利福尼亚州依赖地下水的植被对地下水埋深（DTG）变化的响应。为了最大限度地提高适用性，我们使用Z分数对原始的NDVI和DTG值进行标准化，以确定地下水阈值、地下水目标，并绘制不同生物群落和当地条件下潜在的干旱避难所地图。分析了ZNDVI降至 -1以下时植被受影响的地下水阈值。然后，针对不同状况类别和根系深度的依赖地下水的植被，对ZDTG阈值和目标进行了评估。将ZNDVI分数应用于全州，以确定由地下水支撑的潜在干旱避难所。我们的方法为水资源和保护工作者提供了一种简单而有效的方法，以支持生态系统的用水需求，从而实现生物多样性和可持续水资源管理的目标。