Hydrology under change: long-term annual and seasonal changes in small agricultural catchments in Norway

Abstract

In agricultural catchments, hydrological processes are highly linked to particle and nutrient loss and can lead to a degradation of the ecological status of the water. Global warming and land use changes influence the hydrological regime. This effect is especially strong in cold regions. In this study, we used long-term hydrological monitoring data (22–26 years) from small agricultural catchments in Norway. We applied a Mann–Kendall trend and wavelet coherence analysis to detect annual and seasonal changes and to evaluate the coupling between runoff, climate, and water sources. The trend analysis showed a significant increase in the annual and seasonal mean air temperature. In all sites, hydrological changes were more difficult to detect. Discharge increased in autumn and winter, but this trend did not hold for all catchments. We found a strong coherence between discharge and precipitation, between discharge and snow water equivalent and discharge and soil water storage capacity. We detected different hydrological regimes of rain and snow-dominated catchments. The catchments responded differently to changes due to their location and inherent characteristics. Our results highlight the importance of studying local annual and seasonal changes in hydrological regimes to understand the effect of climate and the importance for site-specific management plans.

Advances in Catchment Science, Hydrochemistry, and Aquatic Ecology Enabled by High-Frequency Water Quality Measurements

“…One such approach is spectral decomposition for frequency-dependent water quality fluctuations, i.e., decomposition of variations in concentrations into frequencies and their related amplitudes. , Frequencies with high amplitudes are often linked to periodic processes such as seasonal or diurnal cycles that can be linked to biogeochemical drivers of solute and particulate stream signals . To visualize shifts in frequency-dependent fluctuations over time, wavelet transforms are often used to analyze high-frequency water quality data. ,, The wavelet coherence metric is a way to relate wavelet transformations of different variables during specific months or seasons and can therefore capture interactions (e.g., a relation between a chemical variable and discharge) . Wavelet methods can also play an important role in analyzing time series that are unevenly sampled, whether by design, through equipment failures, or due to extreme conditions (e.g., during seasonal drought or water column freezing).…”

“… 31 To visualize shifts in frequency-dependent fluctuations over time, wavelet transforms are often used to analyze high-frequency water quality data. 38 , 165 , 166 The wavelet coherence metric is a way to relate wavelet transformations of different variables during specific months or seasons and can therefore capture interactions (e.g., a relation between a chemical variable and discharge). 166 Wavelet methods can also play an important role in analyzing time series that are unevenly sampled, whether by design, through equipment failures, or due to extreme conditions (e.g., during seasonal drought or water column freezing).…”

Twenty Years of Catchment Monitoring Highlights the Predominant Role of Long-Term Phosphorus Balances and Soil Phosphorus Status in Affecting Phosphorus Loss in Livestock-Intensive Regions

“…The main soils are classified in the World Reference Base for Soil Resources as Endostagnic Umbrisol, Umbric Endostagnic Podzol, Umbric Gleysol and Sapric Histosol (FAO/ISRIC/ISSS, 1998). The region has a coastal climate, with high annual precipitation and relatively mild winters as compared to many other regions in Norway (Wenng et al, 2021). During 1992-2021, the catchment has an average of 240 growing days, mean annual temperature of 8.3 • C and mean annual precipitation of 1370 mm.…”

Nordic hydrological frontier in the 21st century

“…Climate extremes have led to more frequent floods and landslides and enhanced drought conditions in summer (Lopez et al 2021). This has altered soil moisture patterns, runoff processes (Stonevicius et al 2017), and nutrient and dissolved organic carbon (DOC) export (Øygarden et al 2014;Meriö et al 2019;de Wit et al 2020;Fork et al 2020;Wenng et al 2021aWenng et al , 2021b. High-latitude environments are particularly vulnerable to the impacts of global warming as these regions are experiencing the most evident and rapid warming when compared to other regions of the world.…”

“…In crop production and forested areas, soil moisture conditions during prolonged dry spells and increased evaporation losses due to global warming challenge traditional catchment management (Veijalainen et al 2019;Bakke et al 2020;Levia et al 2020). More frequent periods of wet soils and changes in surface runoff processes will likely result in enhanced nutrient and DOC leaching patterns (Kämäri et al 2018) as well as greenhouse gas (GHG) emissions and transportation processes of suspended sediments (Kämäri et al 2015;Wenng et al 2021aWenng et al , 2021b.…”