Open Access
In-situ assessment of the spatial arrangement of step-pool units on eroded rills
(wiley, 2019) Govers, G.; Campo-Bescós, Miguel; Zubieta Laseca, Elena; Giménez Díaz, Rafael; Ingeniaritza; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; Ingeniería
Open Access
Assessing hillslope-channel connectivity in an agricultural catchment using rare-earth oxide tracers and random forests models
(Universidad de la Rioja, 2017) Masselink, Rens Hein; Temme, A.J.A.M.; Giménez Díaz, Rafael; Casalí Sarasíbar, Javier; Keesstra, Saskia D.; Proyectos e Ingeniería Rural; Landa Ingeniaritza eta Proiektuak; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD
Soil erosion from agricultural areas is a large problem because of off-site effects like the rapid filling of reservoirs. To mitigate the problem of sediments from agricultural areas reaching the channel, reservoirs and other surface areas it is important to understand hillslope-channel connectivity and catchment connectivity. To determine the functioning of hillslope-channel connectivity and the continuation of transport of these sediments in the channel, it is necessary to obtain data on sediment transport from the hillslopes to the channels. Simultaneously, the factors that influence sediment export out of the catchment need to be studied. For measuring hillslope-channel sediment connectivity, rare-earth oxide (REO) tracers were applied to a hillslope in an agricultural catchment in Navarre, Spain, preceding the winter of 2014-2015. The results showed that during the winter no sediment transport from the hillslope to the channel was detected. To test the implication of the REO results at the catchment scale, two contrasting conceptual models for sediment connectivity were assessed using a random forest (RF) machine learning method. The RF method was applied using a 15-year period of measured sediment output at the catchment scale. One model proposes that small events provide sediment for large events, while the other proposes that only large events cause sediment detachment and small events subsequently remove these sediments from near and in the channel. For sediment yield prediction of small events, variables related to large preceding events were the most important. The model for large events underperformed and, therefore, we could not draw any immediate conclusions whether small events influence the amount of sediment exported during large events. Both REO tracers and RF method showed that low intensity events do not contribute any sediments from the hillslopes to the channel in Latxaga catchment. Sediment dynamics are dominated by sediment mobilization during large (high intensity) events. Sediments are for a large part exported during those events, but the system shows a memory of the occurrence of these large events, suggesting that large amounts of sediments are deposited in and near the channel after these events. These sediments are gradually removed by small events. To better understand the delivery if sediments to the channel and how large and small events influence each other, more field data on hillslope-channel connectivity and within-channel sediment dynamics is necessary.
Open Access
On the influence of spatial resolution in soil surface roughness characterization using Tls and Sfm techniques
(IEEE, 2018) Martínez de Aguirre Escobar, Alejandro; Álvarez-Mozos, Jesús; Giménez Díaz, Rafael; Milenković, Milutin; Pfeifer, Norbert; Ingeniería; Ingeniaritza
Soil surface roughness strongly affects the scattering of microwaves and determines the backscattering coefficient observed by SAR (Synthetic Aperture Radar) sensors. The aim of this study is to analyze the influence of the spatial resolution of Terrestrial Laser Scanner (TLS) and Structure from Motion (SfM) techniques to parameterize surface roughness over agricultural soils. Three experimental plots (5 x 5 meters) representing different roughness conditions were measured by TLS and SfM techniques. Roughness parameters (s and l) were calculated from profiles obtained at different spatial resolutions in parallel and in perpendicular to the tillage direction on each plot. The results showed minor differences in the parameters values between both techniques and, in general, a decreasing trend and an increasing trend for lower spatial resolutions for parameter s and l, respectively.
Open Access
Effect of topography on retreat rate of different gully headcuts in Bardenas Reales area (Navarre, Spain)
(Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, 2007) Campo-Bescós, Miguel; Álvarez-Mozos, Jesús; Casalí Sarasíbar, Javier; Giménez Díaz, Rafael; Proyectos e Ingeniería Rural; Landa Ingeniaritza eta Proiektuak
In Northeast Spain, gullying is a widespread phenomenon. This type of erosion is especially intense in Bardenas Reales (Navarre) where at least two major typical kinds of gully headcut are present. A first group developed in soil material (named, conventional gully headcut), and second group of gully headcut with a sandstone layer as a top horizon (named, sandstone gully headcut). In addition, within the former group, we can distinguish a subgroup of gully headcuts developed in soils particularly prone to piping and tunnelling due to the dispersive condition of the materials (named piping associated gully headcut). In this situation, a question arises: to what extent simple topographic parameters account for the retreat rate of the different kind of gully headcuts observed in the region of Bardenas Reales? The aim of this study was to investigate and gain insight in this issue.
Open Access
Dissolved solids and suspended sediment dynamics from five small agricultural watersheds in Navarre, Spain: a 10-year study
(Elsevier, 2019) Merchán Elena, Daniel; Luquin Oroz, Eduardo Adrián; Hernández García, Iker; Campo-Bescós, Miguel; Giménez Díaz, Rafael; Casalí Sarasíbar, Javier; Valle de Lersundi, Jokin del; Ingeniaritza; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; Ingeniería; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Dissolved solids (DS) and suspended sediment (SS) loads are considered relevant environmental problems. They are related to a wide range of on-site and off-site impacts, such as soil erosion or salinization of water bodies. In this study, the dynamics of DS and SS concentrations and loads were assessed in five small watersheds covering representative agricultural land uses in Navarre (Spain). To this end, discharge, DS and SS concentration data were collected during ten hydrological years at each watershed outlet, and loads were computed from discharge and concentration values. DS concentration followed a seasonal pattern imposed by the availability of water, with higher concentrations recorded in low-flow periods and lower concentration in the high-flow period. SS concentration was extremely variable, with a range of 2–4 orders of magnitude in concentration for any specific discharge. Temporal variations (both intra- and inter-annual) in DS loads were explained by differences in runoff, whereas those of SS were not, being the SS loads associated mainly with specific high flow events. These temporal patterns were observed for both agricultural (this study) and non-agricultural (literature) watersheds. From the data in the Navarrese watersheds and those available in the literature, we inferred that agricultural land use, in general, tends to increase the concentration of both DS and SS. Regarding DS and SS yields, the effects of agricultural land use on DS yields are controlled by the changes in runoff rather than the (small) changes in DS concentration. In this sense, land uses changes expected to increase runoff (i.e., a shift from forested to arable or from rainfed to irrigated agriculture) would increase DS yields. On the other hand, agricultural land use tends to increase SS yields, although the effect is highly variable depending on site-specific factors, both natural (e.g., watershed shape) and anthropogenic (e.g., degree of soil conservation practices). In the Navarrese watersheds, DS yields ranged from 1.1 to 2.2 Mg ha−1 year−1 whereas SS yields ranged from 0.3 to 4.3 Mg ha−1 year−1. DS yields seem to dominate under non-agricultural conditions and in most agricultural land uses at the small watershed scale. On the other hand, SS yields dominate in watersheds with increased soil erosion as a consequence of arable land use over erosion-prone watersheds.
Open Access
Evaluation of 2D models for the prediction of surface depression storage using realistic reference values
(Wiley, 2016) Giménez Díaz, Rafael; Mezkiritz Barberena, Irantzu; Campo-Bescós, Miguel; Álvarez-Mozos, Jesús; González de Audícana Amenábar, María; Martínez de Aguirre Escobar, Alejandro; Casalí Sarasíbar, Javier; Proyectos e Ingeniería Rural; Landa Ingeniaritza eta Proiektuak
Depression storage (DS) is the maximum storage of precipitation and runoff in the soil surface at a given slope. The DS is determined by soil roughness that in agricultural soils is largely affected by tillage. The direct measurement of DS is not straightforward because of the natural permeability of the soil. Therefore, DS has generally been estimated from 2D/3D empirical relationships and numerical algorithms based on roughness indexes and height measurements of the soil surface, respectively. The objective of this work was to evaluate the performance of some 2D models for DS, using direct and reliable measurements of DS in an agricultural soil as reference values. The study was carried out in experimental microplots where DS was measured in six situations resulting from the combination of three types of tillage carried out parallel and perpendicular to the main slope. Those data were used as reference to evaluate four empirical models and a numerical method. Longitudinal altitudinal profiles of the relief were obtained by a laser profilometer. Infiltration measurements were carried out before and after tillage. The DS was largely affected by tillage and its direction. Highest values of DS are found on rougher surfaces mainly when macroforms cut off the dominant slope. The empirical models had a limited performance while the numerical method was the most effective, even so, with an important variability. In addition, a correct hydrological management should take into account that each type of soil tillage affects infiltration rate differently.
Open Access
Evaluación de la producción de sedimentos y calidad de las aguas en cuencas agrarias de Navarra
(Universidad de La Rioja, 2012) Giménez Díaz, Rafael; Casalí Sarasíbar, Javier; Díez Beregaña, Javier; Proyectos e Ingeniería Rural; Landa Ingeniaritza eta Proiektuak; Gobierno de Navarra / Nafarroako Gobernua
The Government of Navarre (Spain) established a series of experimental watersheds on different sites of its territory in order to assess the impact of the agricultural activities on the environment. Hydrological/meteorological and water quality data are continuously monitored. In this paper, data recorded –precipitation, runoff, sediment, nitrate and phosphate– in two grain-sown watersheds (La Tejería and Latxaga) and in a third one (Oskotz) covered with forest and pasture (cattle-breeding) with a sub-watershed almost entirely under forest, are analyzed; the information covers a period of ca. 15 years. The inter/intra annual variability of the involved processes are studied as well as their impact on the water quality and on the ecosystem. The majority of the sediments yielded in the watersheds are registered during winter, though most of the erosive rainfalls occurred in summer. This is because of the easy-prone runoff that prevailed during winter due to the (much) higher water content of the soils in this period. The grain-sown watersheds –roughly similar at first view– present however important differences regarding sediment yield: 1800 kg/ha year at La Tejería and only 450 kg/ha year at Latxaga. This could be mainly due to differences in morphology, topography, and amount of stream channel vegetation between both sites. At Oskotz this figures are as a whole lower than those registered in the cultivated watersheds but eventually larger than those at Latxaga; this depending on the forest management (logging). Water quality is seriously affected at La Tejería with nitrate concentration constantly over critical threshold. By contrast, nitrate values are much lower in Latxaga watershed. However, phosphate concentrations were similar in both grain-sown watersheds corresponding to water with a significant risk of eutrophication. The cattle-breeding activity at Oskotz generated unexpected levels of phosphate much higher than those registered in the cultivated wathersheds.
Open Access
Hydrological signatures based on event runoff coefficients in rural catchments of the Iberian Peninsula
(Wolters Kluwer, 2017) Taguas, Encarnación V.; Nadal-Romero, Estela; Ayuso, José L.; Casalí Sarasíbar, Javier; Cid, Patricio; Dafonte, Jorge; Canatário-Duarte, Antonio; Ferreira, Carla S.S.; Giménez Díaz, Rafael; Giráldez Cervera, Juan Vicente; Gómez-Macpherson, Helena; Gómez, Jose A.; González-Hidalgo, J. Carlos; Lana Renault, Noemí; Lucía, Ana; Mateos, Luciano; Pérez, Rafael; Rodríguez-Blanco, M. Luz; Schnabel, Susanne; Serrano-Muela, M. Pilar; Taboada-Castro, M. Mercedes; Zabaleta, Ane; Proyectos e Ingeniería Rural; Landa Ingeniaritza eta Proiektuak
Hydrological signatures are indices that help to describe the behavior of catchments. These indices can also be used to transfer information from gauged to ungauged catchments. In this study, different approaches were evaluated to determine volumetric runoff coefficients in 18 small/ medium experimental gauged catchments of the Iberian Peninsula and to fit runoff calculations based on precipitation data for gauged and ungauged catchments. Using data derived from 1962 events, rainfall-runoff relationships were characterized and compared in order to evaluate the various hydrological response patterns. Volumetric runoff coefficients and cumulative runoff and precipitation ratios of the events that generated runoff (Rcum) minimized the root mean square error. A linear fit for the estimation of Rcum in ungauged atchments was based on mean annual precipitation, rates of infiltration, the fraction of forest-land use, and the catchment channel length. Despite high catchment heterogeneity, Rcum resulted in a suitable parameter to evaluate hydrological variability in rural gauged and ungauged catchments. In 50% of the catchments, the precipitation accounted for less than 50% of the runoff variation. Annual precipitation, antecedent rainfall, and base flow did not have a high significance in rainfall-runoff relationships, which illustrates the heterogeneity of hydrological responses. Our results highlight the need for signature characterizations of small/medium rural catchments because they are the sources of runoff and sediment discharge into rivers, and it is more economical and efficient to take action to mitigate runoff in rural locations.
Open Access
Gully geometry: what are we measuring?
(European Geosciences Union, 2015) Casalí Sarasíbar, Javier; Giménez Díaz, Rafael; Campo-Bescós, Miguel; Proyectos e Ingeniería Rural; Landa Ingeniaritza eta Proiektuak
Much of the research on (ephemeral) gully erosion comprises the determination of the geometry of these eroded channels, especially their width and depth. This is not a simple task due to uncertainty generated by the wide range of variability in gully cross section shapes found in the field. However, in the literature, this uncertainty is not recognized so that no criteria for their measurement are indicated. The aim of this work is to make researchers aware of the ambiguity that arises when characterizing the geometry of an ephemeral gully and similar eroded channels. In addition, a measurement protocol is proposed with the ultimate goal of pooling criteria in future works. It is suggested that the geometry of a gully could be characterized through its mean equivalent width and mean equivalent depth, which, together with its length, define an “equivalent prismatic gully” (EPG). The latter would facilitate the comparison between different gullies.
Open Access
Progress in gully erosion research: IV International Symposium on Gully Erosion
(Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, 2007) Casalí Sarasíbar, Javier; Giménez Díaz, Rafael; Proyectos e Ingeniería Rural; Landa Ingeniaritza eta Proiektuak
The classic forms of water erosion of the soil comprise sheet, rill, and gully erosion. According to the concept most generalized, in sheet erosion, thin layers of material are uniformly removed from the soil surface due to the action of an overland flow, in a homogeneous manner, over the area affected. This results in a normally very gradual and inappreciable loss of soil. However, in rill and gully erosion, the soil loss is caused by the intense action of a concentrated flow, which thus triggers the formation of small or large channels, i.e. rills or gullies, although the mechanisms implicated in either form of concentrated flow erosion are not identical. One of the main differences probably lies in the (much) greater interrelation between the roughness of the channel bed and the hydraulics of the water flow observed in a eroded rill, with respect to what occurs in a typical gully. So, the latter, as a physical process, deserves a special and specific study. Gully erosion, of world-wide importance, is catalogued by some of the principal centres devoted to soil resource conservation as being the foremost problem to be solved. As it is one of the most serious forms of water erosion, this phenomenon is capable of generating major soil losses even though it covers limited land surfaces. Additionally, the damage caused by this type of erosion frequently spreads beyond the area directly affected, i.e. through the siltation of lakes and reservoirs due to the large amounts of sediments it originates. Nevertheless, gully erosion has not received the attention that it warrants from the scientific community. For instance, a rapid search through any important virtual library shows that only less than 10% of soil erosion studies published up to now in international scientific journals deal directly and specifically with gully erosion. More research and surveys are required in order to obtain a better understanding of the physical mechanisms involved in this type of erosion, with the ultimate aim of developing accurate prediction algorithms and efficient control and damage prevention systems. In fact, there are so many unanswered questions on this important environment topic that scientists all over the world have been holding periodic meetings, in which the latest knowledge and advances in the study of gully erosion have been expounded. The first of these meetings was held in Leuven (Belgium) in 2000, the second in Sicuani (China) in 2002 and the third in Oxford, Mississippi (U.S.A.) in 2004. On that last occasion, the participants proposed that Pamplona (Spain) should be the seat of the following meeting, to be held in September 2007. This book contains the abstracts both from the key speeches and from the contributions presented in the IV International Symposium on Gully Erosion held in Pamplona, in September, 2007.