122 research outputs found
Characterization of soil specific degradation for the northern region of Morocco
LâĂ©rosion hydrique est un processus majeur de dĂ©gradation des sols. Au Maroc, elle est considĂ©rĂ©e comme la principale cause de dĂ©sertification. Elle entraĂźne une rĂ©duction du potentiel productif des sols et l'envasement des retenues de barrages conduisant Ă une perte du volume d'eau mobilisable et remettant en cause la durabilitĂ© de ces ouvrages hydrauliques. Des effets nĂ©gatifs sont rĂ©percutĂ©s dans les domaines de la production de l'Ă©nergie Ă©lectrique, de l'approvisionnement en eau potable et de lâirrigation. Face Ă lâampleur de ce flĂ©au, le Maroc doit multiplier ses interventions pour Ă©valuer les consĂ©quences de la dĂ©gradation des sols et mettre au point des programmes de conservation appropriĂ©s. Dans ce contexte, un Ă©chantillon de 15 barrages localisĂ©s au niveau de la rĂ©gion septentrionale du Maroc a Ă©tĂ© sĂ©lectionnĂ© en vue dâanalyser lâenvasement sur des pĂ©riodes de 8 Ă 47 ans. Les donnĂ©es bathymĂ©triques ont Ă©tĂ© fournies par la DRPE (Direction de la Recherche et de la Planification de lâEau). Le prĂ©sent papier a pour objectifs de i) caractĂ©riser la DĂ©gradation SpĂ©cifique (DS) de la rĂ©gion septentrionale du Maroc Ă travers l'Ă©tude de 15 bassins versants ; ii) d'en dĂ©duire une gamme de variabilitĂ© de la DS dans cette rĂ©gion et iii) d'Ă©valuer la pertinence de modĂšles simples basĂ©s sur la surface du bassin, ou la combinaison de la surface et de la lame Ă©coulĂ©e moyenne annuelle, pour prĂ©dire la DS.Lâapproche adoptĂ©e repose sur la confrontation d'une mesure actualisĂ©e de la DĂ©gradation SpĂ©cifique (DS) dĂ©rivĂ©e des levĂ©s bathymĂ©triques avec des Ă©valuations de cette derniĂšre Ă l'aide de modĂšles Ă©tablis pour prĂ©dire lâenvasement des barrages au Maroc. Lâanalyse de lâalluvionnement des retenues de barrages par le dĂ©pouillement des levĂ©s bathymĂ©triques sur des pĂ©riodes allant de 8 Ă 47 ans montre un envasement total moyen annuel dâenviron 0,6*109 m3, soit 13 % de la capacitĂ© totale initiale qui est de lâordre de 4,6*109 m3 et une variabilitĂ© de la dĂ©gradation spĂ©cifique allant de 172 Ă 5365 t km-2an-1, soit un rapport de 1 Ă 31. Enfin, cette Ă©tude montre la trĂšs forte variabilitĂ© des performances de prĂ©diction de la dĂ©gradation spĂ©cifique basĂ©es sur des modĂšles simples utilisant la surface de bassin et la lame Ă©coulĂ©e.
Mots clĂ©s : Ărosion hydrique, Barrages, Envasement, DĂ©gradation SpĂ©cifique, MarocWater erosion is a major process of soil degradation. In Morocco, it is regarded as the principal cause of desertification. It involves a reduction of the production potential of soils and as the silting of dam reservoirs leading to a loss of the amount of mobilizable water and brings up the issue of resilience of these hydraulic infrastructures. Adverse effects are reflected in the domains of energy production and irrigation and drinking water supplies. To face this challenge, Morocco must multiply its interventions to assess the consequences of soil degradation and to develop suitable programs of soil conservation. In this context, a sample of 15 catchment area located in the northern part of Morocco was selected in order to analyze the silting over periods of 8 to 47 years. The bathymetric data was provided by the DRPE (Direction of the Research and the Planning of Water).This paper aims i) to characterize the Specific Degradation (DS) of the northern part of Morocco through the study of 15 catchment areas; ii) to deduce a range of variability from the DS in this area and iii) to assess the relevance of simple models based on basin area, or the combination of basin area and the annual average flow, to predict the DS. The adopted approach is based on the confrontation of a current measurement of the Specific Degradation (DS) derived from the bathymetric surveys with assessments of the latter using models established to predict the silting of dams in Morocco. The analysis of siltation in dam reservoirs by the investigation of bathymetric data over periods from 8 to 47 years, shows an annual average total silting of approximately 0.6*109 m3, that is13% of the initial total capacity which is about 4.6*109 m3 and a variability of the specific degradation ranging from 172 to 5 365 tkm-2yr-1, that is a ratio of1 to 31. To end with, this study shows a significant variability of the performances of prediction of specific degradation based on simple models using the area of watershed and water flow.
Key words: Water erosion, Dams, Silting, Specific degradation, Morocc
Techniques de conservation des eaux et des sols au Maroc: Aperçu et perspectives
The natural fragility of the environment (relief with steep slopes, aggressive rain, fragile substrates) associated with human fragility (poverty, insecurity) lead to the development and the extension of soil degradation. Water erosion concerns all Moroccan mountains and affects land productivity. This has prompted farmers to design and implement land management techniques, which optimize water use and promote rainwater harvesting. Land management institutions in these areas have also carried out soil protection and restoration (DRS) and soil and water conservation (SWC) projects for the same purposes. This study aims to inventory most of soil and water conservation techniques in Morocco through a literature review. It tracks a set of techniques adopted by farmers to remedy the lack of agricultural land, to enhance land conservation and improve its productivity. Many traditional soil and water conservation systems have been described and classified according to local water balance, topography, operation and objectives: impluvium runoff management, water infiltration increase, diversion of excess-runoff and runoff energy dissipation. Perhaps there exist still other installations not quoted here. Their effectiveness depends on multiple factors, which vary in time and space such as the climatic conditions (dryness) and socio-economic (emigration of youth). Key words: Water erosion, Soil and water conservation, Traditional water and soil management techniques, Land management, Water harvesting, MoroccoLa fragilitĂ© naturelle du milieu (relief accidentĂ©, pluies agressives, substrats fragiles) associĂ©e Ă une fragilitĂ© humaine (pauvretĂ©, prĂ©caritĂ©) conduisent Ă lâapparition et lâextension de phĂ©nomĂšnes de dĂ©gradation des sols spectaculaires. LâĂ©rosion hydrique concerne affecte la productivitĂ© une grande partie des terres marocaines. Cette situation a incitĂ© les paysans Ă concevoir et Ă rĂ©aliser des amĂ©nagements pour rĂ©duire les pertes de terres, optimiser lâutilisation des eaux et valoriser les eaux pluviales. Des projets de DĂ©fense et Restauration des Sols (DRS) et de Conservation des Eaux et des Sols (CES) ont Ă©galement Ă©tĂ© conduits par les institutions dâamĂ©nagement des terres dans ces zones pour les mĂȘmes objectifs. Cette Ă©tude vise, Ă travers une recherche bibliographique, Ă inventorier les techniques de conservation des eaux et des sols au Maroc. Elle retrace un ensemble de techniques adoptĂ©es par les agriculteurs pour remĂ©dier au manque de terres agricoles, leur conservation et lâamĂ©lioration de leur productivitĂ©. De nombreux systĂšmes traditionnels de conservation de lâeau et des sols ont Ă©tĂ© dĂ©crits et classĂ©s en fonction du bilan hydrique local, de la topographie, de leur fonctionnement et de leurs objectifs : la capture du ruissellement sous impluvium, lâinfiltration totale de lâeau, la diversion des excĂ©dents dâeau et la dissipation de lâĂ©nergie du ruissellement. Il existe peut-ĂȘtre encore dâautres amĂ©nagements non citĂ©s ici. Leur efficacitĂ© dĂ©pend de multiples facteurs qui varient dans le temps et dans lâespace comme les conditions climatiques (sĂ©cheresse) et socio-Ă©conomiques (Ă©migration des jeunes).
Mots clĂ©s: Ărosion hydrique, Conservation des eaux et sols, Techniques traditionnelles de gestion de lâeau et du sol, AmĂ©nagement et gestion des terres, Collecte des eaux pluviales, Maro
Spatialisation fine des projections climatiques dans le bassin versant du Tleta, Nord Maroc
Local studies of climate change impact require high spatial resolution of climate predictions. Within ALMIRA research project, agronomists and hydrologists wish to integrate climate predictions into their models in order to characterize the behavior of Tleta watershed by 2050. Global and regional climate models can only apprehend it through one or fewer pixels at best. It is also essential to use a statistical downscaling method, which allows for improving spatial resolution. Based on climate predictions from the French ALADIN-Climate model and available climatic series, a processing sequence has been developed to provide spatialized fields of climatic variables over the period 2021-2060 at 1 kmÂČ resolution.
Keywords: Climate predictions, Spatialization, Nakhla Watershed, Rif, MoroccoLes Ă©tudes locales de lâimpact du changement climatique nĂ©cessitent des projections climatiques Ă haute rĂ©solution spatiale. Dans le cadre du projet de recherche ALMIRA, les agronomes et hydrologues souhaitent intĂ©grer Ă leurs modĂšles des projections climatiques afin de caractĂ©riser le fonctionnement du bassin versant du Tleta Ă lâhorizon des annĂ©es 2050. Les modĂšles climatiques globaux et rĂ©gionaux ne peuvent lâapprĂ©hender quâĂ travers un, voire quelques pixels au mieux. Aussi, il est indispensable de pratiquer une descente dâĂ©chelle statistique qui permette dâaffiner la rĂ©solution spatiale. En sâappuyant sur les projections climatiques issues du modĂšle français ALADIN-Climat et des sĂ©riesclimatiques disponibles, une chaĂźne de traitements a Ă©tĂ© dĂ©veloppĂ©e afin de fournir des champs spatialisĂ©s de variables climatiques sur la pĂ©riode 2021-2060 Ă une maille de 1 kmÂČ.
Mots clés : Projections climatiques, Spatialisation, Bassin versant Nakhla, Rif, Maro
Evaluation Des Performances Du Modele Agro-Hydrologique SWAT Ă Reproduire Le Fonctionnement Hydrologique Du Bassin Versant Nakhla (Rif occidental, Maroc)
Une comprĂ©hension de toutes les composantes du bilan hydrique est indispensable pour raisonner les mesures de gestion rationnelle et durable de la ressource en eau. Malheureusement, plusieurs composantes du bilan hydrique ne sont pas facilement mesurables et le recours Ă la modĂ©lisation est souvent nĂ©cessaire. Pour ce faire, le modĂšle SWAT 2012 (Soil and Water Assessment Tool) a Ă©tĂ© mis en oeuvre Ă un pas de temps mensuel et journalier pour Ă©valuer sa capacitĂ© Ă reprĂ©senter le fonctionnement du bassin versant Nakhla, situĂ© Ă 20 kilomĂštres au sud de la ville de TĂ©touan. Le traitement prĂ©alable des donnĂ©es existantes sur le bassin (MNT, pĂ©dologie, images satellitaires, donnĂ©es climatiques) a permis de reproduire les caractĂ©ristiques naturelles du terrain Ă une rĂ©solution spatiale adaptĂ©e aux objectifs de lâĂ©tude. La mĂ©thodologie adoptĂ©e repose sur lâusage du systĂšme dâinformation gĂ©ographique libre (QGIS) combinĂ© avec le modĂšle agro-hydrologique SWAT pour effectuer des opĂ©rations dâanalyse et de modĂ©lisation du fonctionnement hydrologique Ă lâĂ©chelle du bassin versant et lâoutil SWAT-Cup pour optimiser les opĂ©rations dâanalyse de sensibilitĂ© et dâincertitude. Le processus de calibration est rĂ©alisĂ© aux Ă©chelles temporelles mensuelle et journaliĂšre au niveau de la station Timezouk et au cours de trois pĂ©riodes : de 1980 Ă 1983 pour lâinitiation, de 1984 Ă 1987 pour la calibration et de 1988 Ă 1990 pour la validation. Les rĂ©sultats obtenus aprĂšs calage et validation Ă lâĂ©chelle mensuelle montrent une simulation satisfaisante des dĂ©bits puisque la comparaison des dĂ©bits mensuels observĂ©s et simulĂ©s pour la pĂ©riode de calibration a abouti Ă un NSE de 0,83 et un R2 de 0,88 au niveau de la station Timezouk. Les rĂ©sultats Ă lâĂ©chelle journaliĂšre ne sont pas satisfaisant (NSE< 0.5), ce qui montre que la reprĂ©sentation de la dynamique haute-frĂ©quence des flux dâeau doit encore ĂȘtre amĂ©liorĂ©e. A comprehension of all the components of water balance is essential for rational and durable management of the water resource. However, the direct assessment of several components of the water balance is very difficult and the use of modeling is often necessary. SWAT 2012 (Soil and Water Assessment Tool) model was thus implemented on a monthly and daily time steps to assess his ability to reproduce the hydrological functioning for the Nakhla watershed, which is located at 20 kilometers in the south of the city of Tetouan. Treatment of environmental data (MNT, pedology, satellite imagery and climatic data) allowed to describing the natural characteristic of the field at a resolution adapted to the objectives of the study. Adopted methodology consisted in the combined use of the SWAT agro hydrological model implemented in the QGIS geographical information system open source for operations of analysis and modeling of hydrological processes at the level of the watershed area and of SWAT-CUP tool to optimize the operations of sensitivity and uncertainty analysis. The calibration process was performed on two temporal scales; monthly and daily; and on the stations Timezouk; and over three periods: warm-up period from 1980 to 1983, calibration period from 1984 to 1987, and the validation period from 1988 to 1990. The results acquired after calibration and validation at monthly time step were satisfactory and presented good level of realism in the simulation of the discharge. The comparison of the monthly observed and simulated discharges for the period of calibration gave a NSE of 0.83 and R2 of 0.88 at the Timezouk station. Nevertheless, daily results are not satisfactory (NSE< 0.5), thus further improvements are required to better simulate the processes at a finer time step
Impact Du Changement Climatique Sur LâĂ©volution De L'Ă©rosivitĂ© Des Pluies Dans Le Rif Occidental (Nord Du Maroc)
The rainfall erosivity factor (R factor in Universal Soil Loss Equation), denoting rain energy, is a key factor for soil loss modeling. Its present and future estimation is thus significant for any action related to soil and water conservation and planning. The extended series of precipitations at high temporal resolution, essential to its evaluation, are not readily available in Morocco. The objective of this study is to predict the evolution of rainfall erosivity by 2080 in the Western Rif, based on predictions of daily rain provided by the General Climatic Models (GCMs). To reflect the seasonal variability of rainfall, and thus of R factor, a series of instantaneous rain measured over 35 consecutive years was used to monthly calibrate a model to calculate erosivity based of daily rainfall. The application of this model to the predictions of different GCMs and for various scenarios of climate evolution in Western Rif shows a weak evolution of erosivity on an annual timescale but a very strong evolution of the latter according to seasons with a reduction in R factor during winter and spring, and a pronounced increase during summer and autumn. This discernable change of the seasonality of rainfall erosivity is very useful for adjusting the evolution of agricultural practices and for selecting appropriate soil protection measures
Distinct and combined impacts of climate and land use scenarios on water availability and sediment loads for a water supply reservoir in northern Morocco
The objective of this study was to examine the impacts of climate and land use changes on water
availability and sediment loads for a water supply reservoir in northern Morocco using data-intensive
simulation models in a data-scarce region. Impacts were assessed by comparing the simulated water
and sediment entering the reservoir between the future period 2031e2050 and the 1983e2010 reference
period. Three scenarios of land use change and two scenarios of climate change were developed in the
Tleta watershed. Simulations under current and future conditions were performed using the Soil and
Water Assessment Tool (SWAT) model. The simulations showed that climate change will lead to a significant
decrease in the annual water supply to the reservoir ( 16.9% and 27.5%) and in the annual
volume of sediment entering the reservoir ( 7.4% and 12.6%), depending on the climate change scenarios
tested. The three scenarios of land use change will lead to a moderate change in annual water
inflow into the reservoir (between 6.7% and ĂŸ6.2%), while causing a significant decrease in sediment
entering the reservoir ( 37% to 24%). The combined impacts of climate and land use changes will cause
a reduction in annual water availability ( 9.9% to 33.3%) and sediment supplies ( 28.7% to 45.8%). As
a result, the lifetime of the reservoir will be extended, but at the same time, the risk of water shortages
will increase, especially from July to March. Therefore, alternative water resources must be considered.info:eu-repo/semantics/publishedVersio
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
Relationship of Weather Types on the Seasonal and Spatial Variability of Rainfall, Runoff, and Sediment Yield in the Western Mediterranean Basin
Rainfall is the key factor to understand soil erosion processes, mechanisms, and rates. Most research was conducted to determine rainfall characteristics and their relationship with soil erosion (erosivity) but there is little information about how atmospheric patterns control soil losses, and this is important to enable sustainable environmental planning and risk prevention. We investigated the temporal and spatial variability of the relationships of rainfall, runoff, and sediment yield with atmospheric patterns (weather types, WTs) in the western Mediterranean basin. For this purpose, we analyzed a large database of rainfall events collected between 1985 and 2015 in 46 experimental plots and catchments with the aim to: (i) evaluate seasonal differences in the contribution of rainfall, runoff, and sediment yield produced by the WTs; and (ii) to analyze the seasonal efficiency of the different WTs (relation frequency and magnitude) related to rainfall, runoff, and sediment yield. The results indicate two different temporal patterns: the first weather type exhibits (during the cold period: autumn and winter) westerly flows that produce the highest rainfall, runoff, and sediment yield values throughout the territory; the second weather type exhibits easterly flows that predominate during the warm period (spring and summer) and it is located on the Mediterranean coast of the Iberian Peninsula. However, the cyclonic situations present high frequency throughout the whole year with a large influence extended around the western Mediterranean basin. Contrary, the anticyclonic situations, despite of its high frequency, do not contribute significantly to the total rainfall, runoff, and sediment (showing the lowest efficiency) because of atmospheric stability that currently characterize this atmospheric pattern. Our approach helps to better understand the relationship of WTs on the seasonal and spatial variability of rainfall, runoff and sediment yield with a regional scale based on the large dataset and number of soil erosion experimental stations.Spanish Government (Ministry of Economy and Competitiveness, MINECO) and FEDER Projects: CGL2014 52135-C3-3-R, ESP2017-89463-C3-3-R, CGL2014-59946-R, CGL2015-65569-R, CGL2015-64284-C2-2-R, CGL2015-64284-C2-1-R, CGL2016-78075-P, GL2008-02879/BTE, LEDDRA 243857, RECARE-FP7, CGL2017-83866-C3-1-R, and PCIN-2017-061/AEI. Dhais Peña-Angulo received a âJuan de la Ciervaâ postdoctoral contract (FJCI-2017-33652 Spanish Ministry of Economy and Competitiveness, MEC). Ana Lucia acknowledge the "Brigitte-Schlieben-Lange-Programm". The âGeoenvironmental Processes and Global Changeâ (E02_17R) was financed by the AragĂłn Government and the European Social Fund. JosĂ© AndrĂ©s LĂłpez-TarazĂłn acknowledges the Secretariat for Universities and Research of the Department of the Economy and Knowledge of the Autonomous Government of Catalonia for supporting the Consolidated Research Group 2014 SGR 645 (RIUS- Fluvial Dynamics Research Group). Artemi CerdĂ thank the funding of the OCDE TAD/CRP JA00088807. JosĂ© MartĂnez-Fernandez acknowledges the project Unidad de Excelencia CLU-2018-04 co-funded by FEDER and Castilla y LeĂłn Government. Ane Zabaleta is supported by the Hydro-Environmental Processes consolidated research group (IT1029-16, Basque Government). This paper has the benefit of the Lab and Field Data Pool created within the framework of the COST action CONNECTEUR (ES1306)
Relationship of Weather Types on the Seasonal and Spatial Variability of Rainfall, Runoff, and Sediment Yield in the Western Mediterranean Basin
Rainfall is the key factor to understand soil erosion processes, mechanisms, and rates. Most research was conducted to determine rainfall characteristics and their relationship with soil erosion (erosivity) but there is little information about how atmospheric patterns control soil losses, and this is important to enable sustainable environmental planning and risk prevention. We investigated the temporal and spatial variability of the relationships of rainfall, runoff, and sediment yield with atmospheric patterns (weather types, WTs) in the western Mediterranean basin. For this purpose, we analyzed a large database of rainfall events collected between 1985 and 2015 in 46 experimental plots and catchments with the aim to: (i) evaluate seasonal differences in the contribution of rainfall, runoff, and sediment yield produced by the WTs; and (ii) to analyze the seasonal efficiency of the different WTs (relation frequency and magnitude) related to rainfall, runoff, and sediment yield. The results indicate two different temporal patterns: the first weather type exhibits (during the cold period: autumn and winter) westerly flows that produce the highest rainfall, runoff, and sediment yield values throughout the territory; the second weather type exhibits easterly flows that predominate during the warm period (spring and summer) and it is located on the Mediterranean coast of the Iberian Peninsula. However, the cyclonic situations present high frequency throughout the whole year with a large influence extended around the western Mediterranean basin. Contrary, the anticyclonic situations, despite of its high frequency, do not contribute significantly to the total rainfall, runoff, and sediment (showing the lowest efficiency) because of atmospheric stability that currently characterize this atmospheric pattern. Our approach helps to better understand the relationship of WTs on the seasonal and spatial variability of rainfall, runoff and sediment yield with a regional scale based on the large dataset and number of soil erosion experimental stations
- âŠ