Stream water quality is controlled by the interaction of natural and anthropogenic factors over a range of temporal and spatial scales. Among these anthropogenic factors, land cover changes at catchment scale can affect stream water quality. This work aims to evaluate the influence of land use and seasonality on stream water quality in a representative tropical headwater catchment named as Córrego Água Limpa (Sao Paulo, Brasil), which is highly influenced by intensive agricultural activities and urban areas. Two systematic sampling approach campaigns were implemented with six sampling points along the stream of the headwater catchment to evaluate water quality during the rainy and dry seasons. Three replicates were collected at each sampling point in 2011. Electrical conductivity, nitrates, nitrites, sodium superoxide, Chemical Oxygen Demand (DQO), colour, turbidity, suspended solids, soluble solids and total solids were measured. Water quality parameters differed among sampling points, being lower at the headwater sampling point (0m above sea level), and then progressively higher until the last downstream sampling point (2500m above sea level). For the dry season, the mean discharge was 39.5ls (from April to September) whereas 113.0ls were averaged during the rainy season (from October to March). In addition, significant temporal and spatial differences were observed (P<0.05) for the fourteen parameters during the rainy and dry period. The study enhance significant relationships among land use and water quality and its temporal effect, showing seasonal differences between the land use and water quality connection, highlighting the importance of multiple spatial and temporal scales for understanding the impacts of human activities on catchment ecosystem services.

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In recent decades, the dynamics of global change in developed countries has led to significant alterations in the hydrological and sediment dynamics of terraced land. Agricultural terraces were built to control overland flow and prevent erosion, acting as buffers and barriers throughout the sediment cascading system. Their abandonment and degradation increase the sensitivity of the catchment, promoting the collapse of dry‐stone walls and the reworking of stored sediment. In this study, a geomorphometric index of connectivity—derived from high‐resolution LiDAR data (0.9 pt/m, RMSE < 0.2 m)—analysed the spatial patterns of structural connectivity in a small Mediterranean catchment (4.8 km2) characterized by a massive presence of terraces (37% of the surface area). The morphological characteristics of these anthropogenic features generated a dual effect: (a) general disconnectivity between different compartments of the catchment and (b) concentration of water and sediment flows along preferential pathways promoted by a cascade effect of collapse within the terraced areas. The fieldwork found that 73% of wall collapses were located on these pathways that showed high index of connectivity values (>Q8). This spatial matching was related to feedback dynamics between structural and functional connectivity, in which the failure of walls increases the concentration of runoff, which in turn accelerates the hydraulic processes causing their collapse. Identifying the most connected pathways within the most vulnerable structures in an integrated analysis could be a cost‐effective strategy for establishing priority areas for the management of terraced lands.

The aim of this study is to analyze suspended sediment transport in a Mediterranean agricultural catchment under traditional soil and water conservation practices. Field measurements were conducted in Can Revull, a small ephemeral catchment (1.03 km 2 ) on the island of Mallorca. This study uses continuous turbidity records to analyse suspended sediment transport regimes, construct and interpret multiple regression models of total suspended sediment concentration (SSC) and of SSC related to stormflow discharge, and assess the sediment loads and yields of three hydrological years (2004-2005 to 2006-2007). An annual average SSC of 17.3 mg l −1 , with a maximum of 2270 mg l −1 , was recorded in the middle of the winter period when rainfall intensities are high and headwater slopes are ploughed and thus bare. Strong seasonal contrasts of baseflow dynamics associated with different degrees of dilution provide a large scatter in SSC and in the derived rating curves, reflecting that other factors control the supply of suspended sediment. Multiple regression models identify rainfall intensity as the most significant variable in sediment supply. However, under baseflow conditions, physical and biological processes generate sediment in the channel that is subsequently removed during high flow. In contrast, when baseflow is not present, rainfall intensity is the only process that supplies sediment to the channel, mostly from hillslopes. Considering the study period as average in terms of total annual rainfall and intensities, suspended sediment yields were an order of magnitude lower than those obtained in other Mediterranean catchments, a factor that can be related to the historical use of soil conservation practices. under forest land use. Rainfall data series between 1988 and 2001 years recorded at the Porreres rain gauge, located 7 km from the Can Revull gauging station (Figure 1), allow us to verify that the rainfall intensities for the entire study period [2004][2005][2006][2007] are representative of the long-term record: the average of the maximum 30-min rainfall intensities at the reference site was 27·1 mm h -1 (YACU, 2002), whereas Figure 4. Summary of sediment load and runoff figures obtained for the study period (2004-2007): (a) average monthly yields of runoff and SS and associated coefficient of variation; (b) relative importance of seasonal SS load for each hydrological year and for the whole study period;(c) relative importance of maximum daily runoff and sediment load by season; (d) total cumulative sediment load duration curve.

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In July 2013, a wildfire severely affected the western part of the island of Mallorca (Spain). During the first three post‐fire hydrological years, when the window of disturbance tends to be more open, the hydrological and sediment delivery processes and dynamics were assessed in a representative catchment intensively shaped by terracing that covered 37% of its surface area. A nested approach was applied with two gauging stations (covering 1.2 km2 and 4.8 km2) built in September 2013 that took continuous measurements of rainfall, water and sediment yield. Average suspended sediment concentration (1503 mg L−1) and the maximum peak (33 618 mg L−1) were two orders of magnitude higher than those obtained in non‐burned terraced catchments of Mallorca. This factor may be related to changes in soils and the massive incorporation of ash into the suspended sediment flux during the most extreme post‐fire event; 50 mm of rainfall in 15 min, reaching an erosivity of 2886 MJ mm ha−1 h−1. Moreover, hysteretic counter‐clockwise loops were predominant (60%), probably related to the increased sensitivity of the landscape after wildfire perturbation. Though the study period was average in terms of total annual precipitation (even higher in intensities), minimal runoff (2%) and low sediment yield (6.3 t km−2 y−1) illustrated how the intrinsic characteristics of the catchment, i.e. calcareous soils, terraces and the application of post‐fire measures, limited the hydrosedimentary response despite the wildfire impact. Copyright © 2017 John Wiley & Sons, Ltd.

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