ScenaLand: a simple methodology for developing land use and management scenarios

Scenarios serve science by testing the sensitivity of a system and/or society to adapt to the future. In this study, we present a new land use scenario methodology called ScenaLand. This methodology aims to develop plausible and contrasting land use and management (LUM) scenarios, useful to explore how LUM (e.g. soil and water conservation techniques) may afect ecosystem services under global change in a wide range of environments. ScenaLand is a method for constructing narrative and spatially explicit land use scenarios that are useful for end-users and impact modellers. This method is innovative because it merges literature and expert knowledge, and its low data requirement makes it easy to be implemented in the context of inter-site comparison, including global change projections. ScenaLand was developed and tested on six diferent Mediterranean agroecological and socioeconomic contexts during the MASCC research project (Mediterranean agricultural soil conservation under global change). The method frst highlights the socioeconomic trends of each study site including emerging trends such as new government laws, LUM techniques through a qualitative survey addressed to local experts. Then, the method includes a ranking of driving factors, a matrix about land use evolution, and soil and water conservation techniques. ScenaLand also includes a framework to develop narratives along with two priority axes (contextualized to environmental protection vs. land productivity in this study). In the context of this research project, four contrasting scenarios are proposed: S1 (business-as-usual), S2 (market-oriented), S3 (environmental protection), and S4 (sustainable). Land use maps are then built with the creation of LUM allocation rules based on agroecological zoning. ScenaLand resulted in a robust and easy method to apply with the creation of 24 contrasted scenarios. These scenarios come not only with narratives but also with spatially explicit maps that are potentially used by impact modellers and other endusers. The last part of our study discusses the way the method can be implemented including a comparison between sites and the possibilities to implement ScenaLand in other contexts.info:eu-repo/semantics/publishedVersio

Soft Water Level Sensors for Characterizing the Hydrological Behaviour of Agricultural Catchments

An innovative soft water level sensor is proposed to characterize the hydrological behaviour of agricultural catchments by measuring rainfall and stream flows. This sensor works as a capacitor coupled with a capacitance to frequency converter and measures water level at an adjustable time step acquisition. It was designed to be handy, minimally invasive and optimized in terms of energy consumption and low-cost fabrication so as to multiply its use on several catchments under natural conditions. It was used as a stage recorder to measure water level dynamics in a channel during a runoff event and as a rain gauge to measure rainfall amount and intensity. Based on the Manning equation, a method allowed estimation of water discharge with a given uncertainty and hence runoff volume at an event or annual scale. The sensor was tested under controlled conditions in the laboratory and under real conditions in the field. Comparisons of the sensor to reference devices (tipping bucket rain gauge, hydrostatic pressure transmitter limnimeter, Venturi channels…) showed accurate results: rainfall intensities and dynamic responses were accurately reproduced and discharges were estimated with an uncertainty usually acceptable in hydrology. Hence, it was used to monitor eleven small agricultural catchments located in the Mediterranean region. Both catchment reactivity and water budget have been calculated. Dynamic response of the catchments has been studied at the event scale through the rising time determination and at the annual scale by calculating the frequency of occurrence of runoff events. It provided significant insight into catchment hydrological behaviour which could be useful for agricultural management perspectives involving pollutant transport, flooding event and global water balance

Contamination des eaux de rivière d\u27un bassin versant guadeloupéen (Pérou, Capesterre Belle-Eau, Guadeloupe)

L\u27étude conduite sur une année hydrologique met en évidence les différents processus expliquant la réponse hydrologique à l\u27échelle du bassin versant de la rivière Pérou et caractérise les voies de circulation de la CLD depuis les sols jusqu\u27aux eaux de rivières. Elle souligne la nécessité de considérer l\u27écoulement de surface, sub-surfacique et de profondeur dont l\u27importance varie selon les zones du bassin. Finalement, cette représentation du fonctionnement hydrologique du bassin ouvre des perspectives quant à la modélisation de la dynamique de contamination des eaux à la CLD

A soft hydrological monitoring approach for comparing runoff on a network of small poorly gauged catchments

Contact: [email protected] in many parts of the world are either ungauged or poorly gauged, and the dominant processes governing their streamflow response are still poorly understood. The analysis of runoff coefficients provides essential insight into catchment response, particularly if both range of catchments and a range of events are compared. This paper investigates how well the hydrological runoff of 11 small, poorly gauged catchments with ephemeral streams (0Ð1-0Ð6 km2) can be compared using estimated runoff with the associated uncertainty. Data of rainfall and water depth at a catchment’s outlet were recorded using automatic logging equipment during 2008-2009. The hydrological regime is intermittent and the annual precipitation ranged between 569 and 727 mm. Discharge was estimated using Manning’s equation and channel cross-section measurements. Innovative work has been performed under controlled experimental conditions to estimate Manning’s coefficient values for the different cover types observed in studied streams: non-aquatic vegetations (giant reed, bramble and thistle), grass and coarse granular deposits. The results show that estimates derived using roughness coefficients differ from those previously established for larger streams with aquatic vegetation. Catchment runoff was compared at both the event and the annual scale. The results indicate significant variability between the catchment’s responses. This variability allows for classification in spite of all the uncertainty associated with runoff estimation. This study highlights the potential of using a network of poorly gauged catch ments. From almost no catchment understanding the proposed methodology allows to compare poorly gauged catchments and highlights similarity/dissimilarity between catchment response

Frequency of runoff occurrence in ephemeral catchments in France

International audienc

Framework to guide the choice of the hydrologic model for applications on gauged, poorly gouged and ungauged small catchments : case of natural vc farmed catchments

International audienc

Soil and river contamination patterns of chlordecone in a tropical volcanic catchment in the French West Indies (Guadeloupe)

The aim of this study was to identify primary flow paths involved in the chlordecone (CLD) river contamination and quantify the CLD fluxes to assess CLD pollution levels and duration according to a typical catchment of the banana cropping area in the French Indies (Guadeloupe): the Perou Catchment (12 km(2)) characterized by heavy rainfall (5686 mm year(-1)). Three sub-catchments (SC1, SC2 and SC3) were studied during the hydrological year 2009-2010: a pedological survey combined with a spatialized hydrochemical approach was conducted. The average soil concentration is higher in the Perou Catchment (3400 mu g kg(-1)) than in the entire banana cropping area in Guadeloupe (2100 mu g kg(-1)). The results showed that CLD stocks in soils vary largely among soil types and farming systems: the weakest stocks are located upstream in SC1 (5 kg ha(-1)), where a majority of the area is non-cultivated; medium stocks are located in Nitisols downstream in SC3 (9 kg ha(-1)); and the greatest stocks are observed in SC2 on Andosols (12 kg ha(-1)) characterized by large farms. The annual water balance and the hydro-chemical analysis revealed that the three sub-catchments exhibited different behaviors. Perou River contamination was high during low flows, which highlighted that contamination primarily originated from groundwater contributions. The results showed that only a small part of the catchment (SC2), contributing little to the water flow, comprises a major CLD contribution, which is in agreement with the highly contaminated andosol soils observed there. Another significant result considers that at least 50 years would be required to export the totality of the actual CLD soil stocks retained in the topsoil layer. The actual time for soil remediation will however be much longer considering (i) the necessary time for the chlordecone to percolate and be stored in the shallow aquifers and (ii) its travel time to reach the river.rights reserved

Salinisation des eaux et des sols en zone littorale méditerranéenne : état, pratiques et trajectoires d’évolution

National audienc

Soil Aggregate Stability in Salt-Affected Vineyards: Depth-Wise Variability Analysis

International audienceSoil aggregate stability is an ideal integrative soil quality indicator, but little is known about the relevance of such an indicator with soil depth for salt-affected soils. The objective of this study was to determine soil aggregate stability and identify preponderant aggregation factors, both in topsoil and subsoil horizons in salt-affected conditions. We conducted field investigations by describing soil profiles in pedological pits and by collecting soil samples from different field units. Soils were sampled within different soil horizon types, from superficial tilled organo-mineral horizons to mineral horizons. For all soil samples, we determined the mean weight diameter (MWD) as an indicator of soil aggregate stability and also determined associated physical and chemical properties in some samples. The measured MWD value from 0.28 mm to 1.10 mm could be categorised as unstable, with MWD values and variability decreasing drastically from the topsoil to the deepest mineral horizons. Analysis of MWD in relation to physical and chemical properties suggested that the variability in the MWD value of A-horizons was influenced by both clay fraction abundance and soil organic carbon (SOC) content and the nature of the agricultural practices, while at deeper B-horizons, the decrease in SOC content and the variability in other soil properties with soil depth could be used to explain the overall low aggregate stability. In this study, investigations of soil pits coupled with measurements of soil aggregate stability indicated that it could be possible to restore soil structure quality by limiting deep soil profile compaction in order to improve salt leaching and exportation