Search results for "hydrology"

Concise review of interrill erosion studies in SE Spain (Alicante and Murcia): erosion rates and progress of knowledge from the 1980s

2005

From the 1980s onward studies on interrill soil erosion were intensified in SE Spain. The main achievements of the research carried out in the field areas of Alicante and Murcia concern: first, (1) the estimation of erosion rates directly in the field under a wide range of methodologies, different scales and different environmental conditions; (2) estimations based on existing models, such as the USLE, carried out for different subcatchments of the Segura and Júcar catchments; and (3) other parametric and physical event-based models have also been calibrated and validated. Second, the progress of the knowledge in understanding erosion mechanisms. New and reviewed concepts regarding mainly h…

Vegetation cover seasonal changes assessment from TM imagery in a semi-arid landscape

2004

This work evaluates the suitability of spectral mixture analysis (SMA) methods to assess vegetation cover seasonal changes in a desertification context. Our main interest is to produce remotely sensed derived maps, sensitive to vegetation activity and quite independent of the soil background. A further aim is to analyse the inter-annual variations of this magnitude for different natural vegetation species, in response to seasonal and climatic changes. Fractional vegetation cover (FVC) was obtained using a Variable Endmember Spectral Mixture Analysis (VESMA) technique. The aim is to identify the main vegetation cover and lithological units and decompose them in separate stages. The use of sp…

STOP 1: Lower Gauja spillway valley at Sigulda

2014

STOP 9: Upper Daugava spillway valley and associated gully network at Vasargelišķi

2014

Hydrological effects of a layer of vegetation ash on underlying wettable and water repellent soil

2012

Abstract Hydrological processes after a wildfire may take place under soil conditions altered by heat and by the presence of ash. Soil and ash interact as a two-layer system with poorly understood hydrological properties, especially when ash covers water repellent soil. Here we quantify the effect of an ash layer (0, 5, 15 and 30 mm depth) covering wettable and water repellent soil on (i) the hydrological response and the mechanism of runoff generation and (ii) the water repellency dynamics, for a rainfall event followed by different drying periods and a second rainfall event. Laboratory rainfall simulation experiments (82.5 mm h − 1 during 40 min) at small plot-scale (0.09 m 2 ) were perfo…

Stemflow determination in forest stands

1997

Abstract A stemflow measurement technique is described, based on: (1) correlations between stemflow volume and tree diameters at breast height (DBH), determined on the basis of a relatively low number of tree samplings; (2) the distribution of trees in the stand relative to their DBH. Stemflow for trees in a stand (mm) can thus be determined from total rainfall (mm). The results were compared to those obtained with two other stemflow determination techniques. The proposed method was found to be more reliable, precise and easier to apply than the standard methods.

Global uptake of carbonyl sulfide (COS) by terrestrial vegetation: Estimates corrected by deposition velocities normalized to the uptake of carbon di…

2005

Abstract. COS uptake by trees, as observed under dark/light changes and under application of the plant hormone abscisic acid, exhibited a strong correlation with the CO2 assimilation rate and the stomatal conductance. As the uptake of COS occurred exclusively through the stomata we compared experimentally derived and re-evaluated deposition velocities (Vd; related to stomatal conductance) for COS and CO2. We show that Vd of COS is generally significantly larger than that of CO2. We therefore introduced this attribute into a new global estimate of COS fluxes into vegetation. The new global estimate of the COS uptake based on available net primary productivity data (NPP) ranges between 0.69-1…

Multi-Temporal Soil Salinity Assessment at a Detailed Scale for Discriminating Halophytes Distribution

2016

A multi-temporal survey of soil salinity in a salt lake, recolonized by halophytes, was performed using electromagnetic induction (EMI) providing volume integrated values of soil apparent electrical conductivity (ECa). Inventories of plant communities were recorded according to the Braun-Blanquet method. In each of six areas monospecific with Suaeda vermiculata, Suaeda vera, Sarcocornia fruticosa, or Arthrocnemun macrostachyum, ECa was measured intensively in two seasons. Mean and range of ECa differ for each plant community. Soil was sampled in the six areas and analyzed for ion composition of the soil saturated paste extract. The electrical conductivity of the saturated paste extract (ECe…

Quick and Slow Components of the Hydrologic Response at the Hillslope Scale

2016

It is widely recognized that the Hortonian mechanism of runoff generation occurs in arid and semi-arid regions, generally characterized by high rainfall intensity on soils exhibiting low infiltrabilities. Differently, in steeply sloping forested watersheds in humid climates, by infiltrating through a highly permeable upper soil horizon, water moves beneath the soil surface determining a slow response. However, in most real cases, for example when in arid regions mountain forested areas take place, both (quick and slow) runoff generation processes coexist and together contribute to the hydrologic hillslope response. In this paper, based on analytical solutions of the hydrologic response, ins…

Identifying a dominant discharge for natural rivers in southern Italy

2012

Abstract Natural rivers are subjected to continuous adjustments in response to any change in the environment. These environmental changes may occur naturally, as in the case of climatic variation or changes in vegetative cover, or may be related to human activities including channelization, damming, bank protection, and bridge construction. Identifying the value of that discharge (‘dominant’ or ‘effective’ discharge, QD) considered responsible for the main changes operated by a river has been a subject of great challenge to scientists and engineers during the last decades. In fact, this threshold value is largely adopted for stream-management decisions, for predicting the stable slope upstr…