Continuous separation of land use and climate effects on the past and future water balance

Abstract

19Understanding the combined and separate effects of climate and land use change on the water cycle is 20 necessary to mitigate negative impacts. However, existing methodologies typically divide data into 21 discrete (before and after) periods, implicitly representing climate and land use as step changes when in 22 reality these changes are often gradual. Here, we introduce a new regression-based methodological 23 framework designed to separate climate and land use effects on any hydrological flux of interest 24 continuously through time, and estimate uncertainty in the contribution of these two drivers. We present 25 two applications in the Yahara River watershed (Wisconsin, USA) demonstrating how our approach can 26 be used to understand synergistic or antagonistic relationships between land use and climate in either the 27 past or the future: (1) historical streamflow, baseflow, and quickflow in an urbanizing subwatershed; and 28(2) simulated future evapotranspiration, drainage, and direct runoff from a suite of contrasting climate and 29 land use scenarios for the entire watershed. In the historical analysis, we show that ~60% of recent 30 streamflow changes can be attributed to climate, with approximately equal contributions from quickflow 31 and baseflow. However, our continuous method reveals that baseflow is significantly increasing through 32 time, primarily due to land use change and potentially influenced by long-term increases in groundwater 33 storage. In the simulation of future changes, we show that all components of the future water balance will 34 respond more strongly to changes in climate than land use, with the largest potential land use effects on 35 drainage. These results indicate that diverse land use change trajectories may counteract each other while 36 the effects of climate are more homogeneous at watershed scales. Therefore, management opportunities to 37 counteract climate change effects will likely be more effective at smaller spatial scales, where land use 38 trajectories are unidirectional. 39

Groundwatersheds of protected areas reveal globally overlooked risks and opportunities

“…No systematic study has investigated the potential for human activities outside of protected areas to have impacts on protected areas through groundwater flow (Figure 1). Lateral groundwater flow supplies a significant proportion of water used by vegetation 16 , and changes in land use or land cover can impact downgradient terrestrial ecosystems by changing the quantity and distribution of groundwater 17,18 . Aquatic ecosystems can also be threatened by human activities transmitted through groundwater flow.…”

Future climate or land use? Attribution of changes in surface runoff in a typical Sahelian landscape

“…Climate change and variability are primarily driven by large scale conditions and result in global and regional substantial changes [Bhagat et al, 2022, Connors et al, 2022, IPCC, 2022. Locally mitigating the harming impacts of climate change on the water cycle could be fostered by informed land use and water management at the community level [Zipper et al, 2018].…”

“…Besides, the capacity of populations living in these regions to adapt to climate change and variability impacts remains low [Serdeczny et al, 2017]. In such droughtprone contexts, improving local resilience through integrated water management should both consider land use decisions, water use and allocation [Belemtougri et al, 2021, Fovet et al, 2021, Kafando et al, 2021, Zipper et al, 2018. This, in turn, requires, at the core, a deeper understanding of the individual and combined contributions of climate and land use changes on the hydrological cycle, which is generally not well assessed, especially for such West African watersheds [Aich et al, 2015, Yira et al, 2017, Yonaba, 2020, Gbohoui et al, 2021.…”

Spatial-temporal evolution and driving factors of water yield in three major drainage basins of Hainan Island based on land use change

“…As human activities increase, land use/land cover change (LUCC) has a direct impact on the landscape pattern, ecosystem service types, and ecological processes of the basin, as well as a significant impact on the basin's water volume and the water cycle, thereby affecting the service function of the entire ecosystem (Balist et al, 2022). Therefore, LUCC is considered the main factor leading to the spatial-temporal evolution of water yield (Zipper et al, 2018;Li et al, 2020). By simulating the long-term spatial-temporal dynamics of water yield under the background of land use change, and identifying the dominant and inferior regions of water yield, it can provide scientific reference for establishing future water resources management strategies (Deng et al, 2021).…”