Preliminary Assessment of Global Lake Water Stress Due to Human Consumption of Renewable Water Resources

Abstract:

Existing studies on global water vulnerability, including the balance between physical abundance and human demand of water resources across space and time, have received increasing attentions. Human water withdrawals stem from both discharge in rivers and stores in lakes, reservoirs, and aquifers. Among them, river discharge and natural groundwater recharge are considered to be the primary circulating or renewable freshwater resources (RFWR) for human use. Excessive human withdrawals from RFWR will not only threaten the sustainability of its own, but also “transfer” the pressure to the already less-sustainable water stores. As important water stores, lakes and reservoirs are an integrated component of the global drainage system. When the local withdrawal of RFWR (e.g., river discharge) exceeds a sustainable threshold, the water storage in lakes and reservoirs may function as an immediate mitigation source. Given continuous population growth and the profound uncertainties from climate change, lake water storage is expected to be increasingly vulnerable to human RFWR consumptions. However, such human-induced vulnerability of lake water storage has not been assessed on a global scale. Here, we aim at applying an integrated method to provide the first global-scale assessment of lake water stress induced by human’s unsustainable usage of RFWR. Specifically, we will evaluate a lake water stress (LWS) index, which quantifies the spatial deficit of RFWR as a proportion of the physical availability of lake water storage. The deficit of RFWR will be evaluated by the amounts of net human water withdrawal (i.e., consumption) that exceed serial critical thresholds of the natural abundance of major RFWR including river discharge and groundwater recharge. Lake water storage will be acquired from the UCLA-KSU circa-2015 global lake inventory, which documents the volume and freshwater/saline type of each inventoried lake/reservoir (> 0.4 ha). The abundance of RFWR and sectoral human water consumptions will be simulated by the PCRasrer Global Water Balance (PCR-GLOBWB) hydrological model. We expect that the spatial details revealed by LWS will provide an important insight into the state of global lake water storage on the context of not only its physical abundance but also human-induced vulnerability of RFWR.