An Attempt to Decompose the Impact of Land Use and Climate Change on Annual Runoff in a Small Agricultural Catchment

Abstract

The aims of this study are: i) to better understand the coupled interactions between land use changes, climate change and the aquatic ecosystem in a small agricultural catchment (<100 km2) with a long observation history (1963–2018) and a known land use history, and ii) to test available approaches to separate land use and climate change impacts on water resources in such a small catchment. The pre- and post-change periods have been separated based on change points and the known land use history. Next, conceptual and analytical approaches were applied to quantify and to distinguish between the impacts of climate and land use changes on annual runoff for these two periods. Over the observation period, both land use changes (increase in forest areas) as well as climate change (a temperature rise and a decrease in annual precipitation) occurred. These changes contributed to a decrease in the average annual runoff by 51.9 mm (49% of the long-term average) during the observation period. The quantified contributions of climate and land use changes to the decrease in the mean annual runoff amount to between 60% and 80% and between 40% and 20%, respectively. (i) The results obtained from different methods were consistent - a change in runoff was primarily caused by shifts in climatic variables. (ii) However, the quantified contributions varied depending on the method applied and the form of the Budyko curve. (iii) Thus, special care should be taken in relation to the selection of the Budyko curve for quantifying these changes. (iv) Knowledge of the water deficit sources can result in better planning of water resources management in such small catchments.

Dynamics of the Natural Afforestation Process of a Small Lowland Catchment and Its Possible Impact on Runoff Changes

“…The analysis of the average annual air temperature at the Puławy meteorological station (Figure 2), located close to the Zagożdżonka river catchment (about 40 km), clearly shows its increase, which corresponds to the results presented for Poland [2]. There is also an increase in the annual evaporation value for the catchment area [13]. However, the evaluation of the long-term series of measurement data (1963-2018) concerning the total annual rainfall in the Zagożdżonka river catchment indicates that, despite the downward tendency (Figure 2), there are no statistically significant changes in their trend [12,31].…”

“…The previous study in the Zagożdżonka catchment shows that the estimated contributions of climate and land-use changes to the decrease in mean annual runoff in the studied catchment amount to between 60% and 80% and between 40% and 20%, respectively [13]. However, the impact may be different depending on local conditions.…”

“…Similar conclusions can be found in the publications of other researchers, especially in the work by Czarnecka and Nidzgorska-Lencewicz [3], which included 38 meteorological stations of the Institute of Meteorology and Water Management-National Research Institute, from the area of Poland (excluding the mountainous are), where none of the analyzed precipitation characteristics showed a statistically significant linear trend, even at the level of α = 0.10 in the period 1951-2010. However, in the prevailing area of the country, a slight tendency of an increase in the precipitation in spring and There is also an increase in the annual evaporation value for the catchment area [13]. However, the evaluation of the long-term series of measurement data (1963-2018) concerning the total annual rainfall in the Zagożdżonka river catchment indicates that, despite the downward tendency (Figure 2), there are no statistically significant changes in their trend [12,31].…”

“…Therefore, arable lands have been partially left as fallow and thus the ecological succession has started. As a result, a rapid increase in the ratio of the forest areas can be observed during the period 2001-2006 [13]. The reasons can be found in the situation of small farms, which in Europe looks unfavorable.…”

Hydrological Responses of Watershed to Historical and Future Land Use Land Cover Change Dynamics of Nashe Watershed, Ethiopia

“…Accordingly, SWAT was implemented for this study based on the criteria specified for the Nashe watershed. Generally, SWAT is physically based, a spatially semidistributed, daily time step parameter model designed to simulate all relevant parameters of a watershed-such as surface runoff, ground water, soil water, and lateral flow [27,28]. The studies conducted on the hydrological processes of watershed based on LULC change shows marked increase in rainy season flow and surface runoff potential in a given watershed that corresponds to the expansion of agricultural land and urban area at the decline of forest cover [2,29,30].…”