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Abstract 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. Highlights • Dissolved solids concentration follows a seasonal pattern. • Suspended sediment concentration was extremely variable. • Dissolved loads behave conservatively with water. • The dissolved load dominated the exportation in most of the cases. • Agricultural land use increases suspended sediment concentration and loads. [ABSTRACT FROM AUTHOR]

Abstract: Tree-ring analysis has been demonstrated to be a useful tool for palaeohydrology. Selecting suitable study areas is the first step in palaeoflood research using tree-ring techniques. Objective methods are needed to facilitate exploration and subsequent location of basins where sediment-laden flash floods are likely and that also have tree species suitable for dendrogeomorphological research in a palaeohydrological context. This paper presents a novel methodology for selecting preliminary suitable watersheds for dendrogeomorphological palaeoflood research in central Spain. Geographical information systems (GIS) provide decision-makers with a powerful set of tools for the manipulation and analysis of spatial information. Using GIS tools and basic thematic maps, we defined three different indexes concerning the occurrence of dendrogeomorphological evidence. A Consensus Decision Making procedure (CDM) was carried out in order to weight each factor individually prior to combining the factors. As a result, we obtained information about the most appropriate watersheds for palaeoflood research using tree-ring analysis. A total of 189 watersheds appeared to be highly interesting for tree-ring studies. Of these only 17 have flow gauges, so data concerning frequency and magnitude of floods in basins without gauges could potentially be provided by dendrogeomorphological studies. In order locate such sites and to carry out such studies more efficiently, a more objective methodology for selecting watersheds for tree-ring studies is presented. [Copyright &y& Elsevier]