Runoff and sediment yield from a small watershed in southeastern Spain (Lanjarón): implications for water quality

Abstract

sediment yield from a small watershed in southeastern Spain (Lanjarón): implications for water quality. Hydrological Sciences Journal, 57 (8), 1610-1625. Abstract This study presents an analysis of three hydrological years (2007/08, 2008/09 and 2009/10) of precipitation, runoff and sediment yield collected from a small (669.7 ha) semi-arid watershed in southeastern Spain (Lanjarón). At the watershed outlet the runoff, suspended sediment concentration, total solute concentrations and dissolved nutrients (N-NO 3 , N-NH 4 , H 2 PO 4 and K) in streamflow were continuously monitored. The runoff was highly variable, ranging between 53.4 and 154.7 mm year -1 , with an average of 97.6 mm year -1 . In contrast, sediment yields were more regular, averaging 1.8 Mg ha -1 year -1 . The hydrological response of the watershed depended mainly on rainfall intensity. Formerly, 32% of the watershed was forested and runoff was more regular, despite the typical Mediterranean rainfall cycle; however, due to forest area reduction to 17% and the increase in abandoned farmland area (18%) in recent decades, the runoff variability has increased. Greater amounts of solutes (32.7 Mg ha -1 year -1 ) were exported, so that this water is considered as poor for irrigation use. The temporal nutrient export was related to seasonal discharge fluctuations as well as daily concentrations. In addition, the nutrient concentrations of the water discharged were lower than threshold limits cited in water-quality standards for agricultural use and for potable water, with the exception of K (65.9 mg L -1 ), which may degrade surface waters as well as irrigated soils. Thus, hydrological and erosive processes depended on the watershed features, but also on prior conditions in combination with the characteristics of rainfall episodes. Runoff and sediment yield from a small watershed in southeastern Spain 1611 qualité de l'eau pour un usage agricole ainsi que pour l'eau potable, à l'exception de K (65,9 mg L -1 ), ce qui peut dégrader les eaux de surface ainsi que les sols irrigués. Ainsi, les processus hydrologiques et érosifs dépendent des caractéristiques du bassin, mais aussi des conditions antérieures, combinées aux caractéristiques des épisodes pluvieux.

Application of a tank model to assess the flood-control function of a terraced paddy field

“…The evaluation of flood risk due to changes in management practices or land use for sloping agricultural fields is crucial (Cheng et al 2008, Durán et al 2012, and poor management and abandoned cultivation of terraced paddy fields can be regarded as the major contributors of the increase in peak flow in the downstream area. Deepwater management practices may be an excellent approach to increase the water-storage capacity in the remaining floodcultivation terraced paddy fields.…”

Quantifying connectivity and its effects on sediment budgeting for an agricultural basin, Chesapeake Bay Watershed, United States

“…Fine‐grained sediment pollution is regulated by environmental agencies worldwide, including the U.S. Environmental Protection Agency (EPA) (Bergmann & Maass, 2007; U.S. EPA, 1999) because excessive sediment runoff due to anthropogenic activities is a major concern for the ecological health of watersheds (Durán Zuazo et al, 2012; Gellis et al, 2009; Zhou et al, 2017). Sediments, particularly those less than 63 μm in diameter (hereafter referred to as ‘fine sediments’), can reduce streambed oxygenation when deposited in upstream headwaters causing adverse impacts on aquatic ecosystems such as smothering vulnerable fish eggs (Lisle, 1989).…”