Optimization of Modelling Population Density Estimation Based on Impervious Surfaces

Looking beyond MS4 communities: Assessing impervious cover and population dynamics in small towns

Water quality and quantity are strongly influenced by land use and land cover, with impervious surfaces serving as a key indicator of watershed health. Increased imperviousness alters watershed hydrology, shifting it from infiltration-dominant to runoff-dominant, leading to reduced groundwater recharge, higher runoff, increased peak discharge, and channel enlargement. In the United States, policy regarding stormwater management is predominantly focused on towns with populations greater than 10,000. However, any increase in impervious cover can negatively affect hydrology and water quality, and communities with populations smaller than 10,000 often lack the financial and technical resources to mitigate issues from impervious cover. This study examines changes in impervious cover in small towns and HUC-12 watersheds in eastern South Dakota between 2001 and 2019, alongside population changes from 2000 to 2020 in towns with populations under 10,000. Imperviousness changes were evaluated using the NLCD, and population shift was assessed using U.S. census data. A t-test was performed to compare changes over time, followed by linear regression and generalized additive model to examine the effects of population density dynamics and proximity to larger cities on changes in imperviousness. Results reveal significant demographic changes, with more than half of the towns studied experiencing population declines, while those closer to larger cities saw growth. Despite these population declines, many towns saw significant increases in imperviousness, highlighting that population change alone does not fully explain shifts in impervious surfaces and that other factors, such as land-use policies and socio-economic factors, play a significant role. Although small towns contributed modestly to overall watershed imperviousness, more than half (52 %) of these towns had already exceeded the 10 % threshold commonly associated with ecological impairment by 2019. Additionally, the average imperviousness in these towns rose from 9.3 % in 2001 to 12.7 % in 2019, highlighting the need for expanding the focus of stormwater policy beyond larger communities. Interestingly, while imperviousness significantly increased in small towns, most watersheds experienced a decline, and only 28.2 % of watersheds saw increases primarily among those near larger urban centers, underscoring complex spatial patterns in land use. These findings highlight the importance of addressing these challenges with finer-scale watershed delineations, localized management support, and strategies to enhance community resilience and improve water resource management in small towns.

Spatio-temporal Differentiation of Coupling Coordination between Ecological Footprint and Ecosystem Service Functions in the Aksu Region, Xinjiang, China

The ecological footprint and ecosystem service functions in the northwest arid region of China have their unique characteristics and are limited by natural resources. The coordination level between the pressure of human activities on the ecosystem and the ecosystem service capacity can be objectively reflected on by exploring the coupling coordination relationship between these two aspects. This work used the ecological footprint and Integrated Valuation of Ecosystem Services and Trade-offs models to quantitatively analyze the spatial and temporal variations of the ecological footprint and ecosystem service functions in the Aksu region in Xinjiang. A coupling coordination degree model and spatial autocorrelation analysis were used to assess the coupling coordination level and spatial agglomeration characteristics of the regional ecological footprint and ecosystem service functions. The results showed that the ecological footprint of the Aksu region has been high in the northeast and low in the southwest, with noticeable spatial heterogeneity, from 2005 to 2018. Carbon (66.17%) and cropland (26.64%) are the main contributing factors to the regional ecological footprint. The biocapacity is dominated by cropland, built-up land, and forest land. The ecological footprint and biocapacity showed an increasing trend, ranging from an ecological surplus to an ecological deficit, with a continued ecological deficit. The level of ecosystem service functions in the Aksu region was low, with significant spatial variability. The high values were concentrated in the northern part of the region and the Tarim and Hotan River Basins. The coupling coordination level of the ecological footprint and ecosystem service functions in the Aksu area was high in the north and low in the south. The aforementioned coupling coordination level was dominated by the spatial pattern of the ecosystem service functions and had noticeable spatial agglomeration characteristics. The coupling coordination degree of the ecological footprint and water supply function showed an upward trend. By contrast, the coupling coordination degree of the ecological footprint with soil conservation and biodiversity maintenance functions showed a downward trend.