Relationship of Weather Types on the Seasonal and Spatial Variability of Rainfall, Runoff, and Sediment Yield in the Western Mediterranean Basin

Rainfall is the key factor to understand soil erosion processes, mechanisms, and rates. Most research was conducted to determine rainfall characteristics and their relationship with soil erosion (erosivity) but there is little information about how atmospheric patterns control soil losses, and this is important to enable sustainable environmental planning and risk prevention. We investigated the temporal and spatial variability of the relationships of rainfall, runoff, and sediment yield with atmospheric patterns (weather types, WTs) in the western Mediterranean basin. For this purpose, we analyzed a large database of rainfall events collected between 1985 and 2015 in 46 experimental plots and catchments with the aim to: (i) evaluate seasonal differences in the contribution of rainfall, runoff, and sediment yield produced by the WTs; and (ii) to analyze the seasonal efficiency of the different WTs (relation frequency and magnitude) related to rainfall, runoff, and sediment yield. The results indicate two different temporal patterns: the first weather type exhibits (during the cold period: autumn and winter) westerly flows that produce the highest rainfall, runoff, and sediment yield values throughout the territory; the second weather type exhibits easterly flows that predominate during the warm period (spring and summer) and it is located on the Mediterranean coast of the Iberian Peninsula. However, the cyclonic situations present high frequency throughout the whole year with a large influence extended around the western Mediterranean basin. Contrary, the anticyclonic situations, despite of its high frequency, do not contribute significantly to the total rainfall, runoff, and sediment (showing the lowest efficiency) because of atmospheric stability that currently characterize this atmospheric pattern. Our approach helps to better understand the relationship of WTs on the seasonal and spatial variability of rainfall, runoff and sediment yield with a regional scale based on the large dataset and number of soil erosion experimental stations.Spanish Government (Ministry of Economy and Competitiveness, MINECO) and FEDER Projects: CGL2014 52135-C3-3-R, ESP2017-89463-C3-3-R, CGL2014-59946-R, CGL2015-65569-R, CGL2015-64284-C2-2-R, CGL2015-64284-C2-1-R, CGL2016-78075-P, GL2008-02879/BTE, LEDDRA 243857, RECARE-FP7, CGL2017-83866-C3-1-R, and PCIN-2017-061/AEI. Dhais Peña-Angulo received a “Juan de la Cierva” postdoctoral contract (FJCI-2017-33652 Spanish Ministry of Economy and Competitiveness, MEC). Ana Lucia acknowledge the "Brigitte-Schlieben-Lange-Programm". The “Geoenvironmental Processes and Global Change” (E02_17R) was financed by the Aragón Government and the European Social Fund. José Andrés López-Tarazón acknowledges the Secretariat for Universities and Research of the Department of the Economy and Knowledge of the Autonomous Government of Catalonia for supporting the Consolidated Research Group 2014 SGR 645 (RIUS- Fluvial Dynamics Research Group). Artemi Cerdà thank the funding of the OCDE TAD/CRP JA00088807. José Martínez-Fernandez acknowledges the project Unidad de Excelencia CLU-2018-04 co-funded by FEDER and Castilla y León Government. Ane Zabaleta is supported by the Hydro-Environmental Processes consolidated research group (IT1029-16, Basque Government). This paper has the benefit of the Lab and Field Data Pool created within the framework of the COST action CONNECTEUR (ES1306)

Relationship of Weather Types on the Seasonal and Spatial Variability of Rainfall, Runoff, and Sediment Yield in the Western Mediterranean Basin

Rainfall is the key factor to understand soil erosion processes, mechanisms, and rates. Most research was conducted to determine rainfall characteristics and their relationship with soil erosion (erosivity) but there is little information about how atmospheric patterns control soil losses, and this is important to enable sustainable environmental planning and risk prevention. We investigated the temporal and spatial variability of the relationships of rainfall, runoff, and sediment yield with atmospheric patterns (weather types, WTs) in the western Mediterranean basin. For this purpose, we analyzed a large database of rainfall events collected between 1985 and 2015 in 46 experimental plots and catchments with the aim to: (i) evaluate seasonal differences in the contribution of rainfall, runoff, and sediment yield produced by the WTs; and (ii) to analyze the seasonal efficiency of the different WTs (relation frequency and magnitude) related to rainfall, runoff, and sediment yield. The results indicate two different temporal patterns: the first weather type exhibits (during the cold period: autumn and winter) westerly flows that produce the highest rainfall, runoff, and sediment yield values throughout the territory; the second weather type exhibits easterly flows that predominate during the warm period (spring and summer) and it is located on the Mediterranean coast of the Iberian Peninsula. However, the cyclonic situations present high frequency throughout the whole year with a large influence extended around the western Mediterranean basin. Contrary, the anticyclonic situations, despite of its high frequency, do not contribute significantly to the total rainfall, runoff, and sediment (showing the lowest efficiency) because of atmospheric stability that currently characterize this atmospheric pattern. Our approach helps to better understand the relationship of WTs on the seasonal and spatial variability of rainfall, runoff and sediment yield with a regional scale based on the large dataset and number of soil erosion experimental stations

Algunas notas sobre la erosión de suelos en la provincia de Córdoba

The most fertile agricultural lands in Cordoba province are located throughout the Valley and Campiña. Despite their productivity, the Mediterranean climatic conditions impose several constraints (rainfall irregularity, reduced vegetation cover) that contribute to increasing soil loss. Moreover, the hydrological properties of vertic soils (the most frequent soil type in the Campiña, with high clay content and runoff production) along with a soft underlying parent material (marls) may favour the formation of concentrated flow erosion features such as rills and gullies. In many cases involving both annual crops and olive orchards in Cordoba, the degradation of the soil by water erosion has been proven to be well above sustainable rates. This is a consequence of intensive agriculture management, landscape simplification, and the absence of soil conservation practices. In addition, there are several off-site erosion effects such as as reservoir siltation and sediment deposition in riparian areas that lead to the reduction of effective channel sections and hence flooding. The solution to these problems requires the participation of different stakeholders including farmers, researchers, policymakers and technicians, as well as the consideration of economical issues. It is important that feasibility studies on conservation measures include the costs of unmanaged on-site and off-site erosion. According to soil institution reports, these may be within the same order of magnitude as conservation costs. Further coordinated efforts are needed to address this key environmental aspect, despite the fact that there have been some recent advances within the sector

The normalized topographic method: an automated procedure for gully mapping using GIS

Many studies in agricultural areas focus on the place where the head of rills and gullies start, but little information is available on defining their limits in the transversal direction. Here, we compare the ability of image interpretation and terrain analysis to delineate gully limits accurately by using topographical criteria, and we propose an automated procedure for mapping gullies. A 600m-long gully network was surveyed through an airborne campaign in order to obtain a high resolution elevation model (0.06m pixel size) in combination with differential GPS measurements for defining the reference perimeter. The gully was located near the city of Cordoba (southern Spain) with annual crops in a typical Campiña landscape. In all cases, the techniques based on terrain analysis over-performed those requiring visual interpretation of aerial images. Orthophotography interpretation was hindered by the existence of a crop-gully interface covered by weeds, that led mainly to overestimation of the gully area, although different trends were found among operators. 24 The slope criterion used to determine gully areas produced good results for medium-high resolutions, whereas the profile curvature was preferable when only high pixel sizes were available. An optimal resolution of around 0.5m was found for defining the gully perimeter when using topographic factors, showing that intermediate relative resolutions may be the most effective way to describe the geometry of the gully (5-10% of the mean gully width). The automated procedure featured the combination of the slope and the local lowness index and the use of rendering display methods. It proved to be accurate when compared with the terrain analysis methods based on manual digitising and was found to be applicable on the landscape scale. The sequential implementation of the procedure for increasing resolutions improved the accuracy of the gully mapping by adapting the pixel size to the variability of gully dimensions.JRC.H.4-Monitoring Agricultural Resource

Relationship of runoff, erosion and sediment yield to weather types in the Iberian Peninsula

Precipitation has been recognized as one of the main factors driving soil erosion and sediment yield (SY), and its spatial and temporal variability is recognized as one of the main reasons for spatial and temporal analyses of soil erosion variability. The weather types (WTs) approach classifies the continuum of atmospheric circulation into a small number of categories or types and has been proven a good indicator of the spatial and temporal variability of precipitation. Thus, the main objective of this study is to analyze the relationship between WTs, runoff, soil erosion (measured in plots), and sediment yield (measured in catchments) in different areas of the Iberian Peninsula (IP) with the aim of detecting spatial variations in these relationships. To this end, hydrological and sediment information covering the IP from several Spanish research teams has been combined, and related with daily WTs estimated by using the NMC/NCAR 40-Year Reanalysis Project. The results show that, in general, a few WTs (particularly westerly, southwesterly and cyclonic) provide the largest amounts of precipitation; and southwesterly, northwesterly and westerly WTs play an important role in runoff generation, erosion and sediment yield as they coincide with the wettest WTs. However, this study highlights the spatial variability of erosion and sediment yield in the IP according to WT, differentiating (1) areas under the influence of north and/or north-westerly flows (the north coast of Cantabria and inland central areas), (2) areas under the influence of westerly, southwesterly and cyclonic WTs (western and southwestern IP), (3) areas in which erosion and sediment yield are controlled by easterly flows (Mediterranean coastland), and (4) lastly, a transitional zone in the inland northeast Ebro catchment, where we detected a high variability in the effects of WTs on erosion. Overall results suggest that the use of WTs derived from observed atmospheric pressure patterns could be a useful tool for inclusion in future projections of the spatial variability of erosion and sediment yield, as models capture pressure fields reliably

Relationship of weather types on the seasonal and spatial variability of rainfall, runoff, and sediment yield in the western Mediterranean basin

Rainfall is the key factor to understand soil erosion processes, mechanisms, and rates. Most research was conducted to determine rainfall characteristics and their relationship with soil erosion (erosivity) but there is little information about how atmospheric patterns control soil losses, and this is important to enable sustainable environmental planning and risk prevention. We investigated the temporal and spatial variability of the relationships of rainfall, runoff, and sediment yield with atmospheric patterns (weather types, WTs) in the western Mediterranean basin. For this purpose, we analyzed a large database of rainfall events collected between 1985 and 2015 in 46 experimental plots and catchments with the aim to: (i) evaluate seasonal differences in the contribution of rainfall, runoff, and sediment yield produced by the WTs; and (ii) to analyze the seasonal efficiency of the different WTs (relation frequency and magnitude) related to rainfall, runoff, and sediment yield. The results indicate two different temporal patterns: the first weather type exhibits (during the cold period: autumn and winter) westerly flows that produce the highest rainfall, runoff, and sediment yield values throughout the territory; the second weather type exhibits easterly flows that predominate during the warm period (spring and summer) and it is located on the Mediterranean coast of the Iberian Peninsula. However, the cyclonic situations present high frequency throughout the whole year with a large influence extended around the western Mediterranean basin. Contrary, the anticyclonic situations, despite of its high frequency, do not contribute significantly to the total rainfall, runoff, and sediment (showing the lowest efficiency) because of atmospheric stability that currently characterize this atmospheric pattern. Our approach helps to better understand the relationship of WTs on the seasonal and spatial variability of rainfall, runoff and sediment yield with a regional scale based on the large dataset and number of soil erosion experimental stations.Ministerio de Economía y Competitividad | Ref. CGL2014 52135-C3-3-RMinisterio de Economía y Competitividad | Ref. ESP2017-89463-C3-3-RMinisterio de Economía y Competitividad | Ref. CGL2014-59946-RMinisterio de Economía y Competitividad | Ref. CGL2015-65569-RMinisterio de Economía y Competitividad | Ref. CGL2015-64284-C2-2-RMinisterio de Economía y Competitividad | Ref. CGL2015-64284-C2-1-RMinisterio de Economía y Competitividad | Ref. CGL2016-78075-PMinisterio de Economía y Competitividad | Ref. GL2008-02879/BTEEuropean Commission | Ref. LEDDRA 243857Ministerio de Economía y Competitividad | Ref. CGL2017-83866- C3-1-RMinisterio de Economía y Competitividad | Ref. PCIN-2017-061/AEIMinisterio de Economía y Competitividad | Ref. FJCI-2017-33652Gobierno de Aragón | Ref. E02_17RGeneralitat de Catalunya | Ref. 2014 SGR 645Junta de Castilla y León | Ref. CLU-2018-04Gobierno Vasco | Ref. IT1029-16OECD (Biological Resource Management for Sustainable Agricultural Systems) | Ref. OCDE TAD/CRP JA0008880

Spatial variability of the relationships of runoff and sediment yield with weather types throughout the Mediterranean basin

Soil degradation by water is a serious environmental problem worldwide, with specific climatic factors being the major causes. We investigated the relationships between synoptic atmospheric patterns (i.e. weather types, WTs) and runoff, erosion and sediment yield throughout the Mediterranean basin by analyzing a large database of natural rainfall events at 68 research sites in 9 countries. Principal Component Analysis (PCA) was used to identify spatial relationships of the different WTs including three hydro-sedimentary variables: rainfall, runoff, and sediment yield (SY, used to refer to both soil erosion measured at plot scale and sediment yield registered at catchment scale). The results indicated 4 spatial classes of rainfall and runoff: (a) northern sites dependent on North (N) and North West (NW) flows; (b) eastern sites dependent on E and NE flows; (c) southern sites dependent on S and SE flows; and, finally, (d) western sites dependent on W and SW flows. Conversely, three spatial classes are identified for SY characterized by: (a) N and NE flows in northern sites (b) E flows in eastern sites, and (c) W and SW flows in western sites. Most of the rainfall, runoff and SY occurred during a small number of daily events, and just a few WTs accounted for large percentages of the total. Our results confirm that characterization by WT improves understanding of the general conditions under which runoff and SY occur, and provides useful information for understanding the spatial variability of runoff, and SY throughout the Mediterranean basin. The approach used here could be useful to aid of the design of regional water management and soil conservation measures