Morphometric Assessment of Two Watersheds of High Atlas of Morocco Using Remote Sensing and GIS Techniques: What Is the Impact on Surface Water Availability?

The abundance or scarcity of surface water in a watershed is related to environmental factors including its morphology, substrate type, rainfall, slope, and exposure to moist air masses. The combination of these characteristics explains the hydrological behavior of the river network, knowledge of which is important for water resources management. Geographic Information System and Remote Sensing are efficient tools to assess the morphometric characteristic in a watershed. Using these tools, the physical characterization of the two water basins located on either side of the High Atlas of Morocco was investigated in this study. The results show that the Upper Draa basin is characterized by an elongated shape, with a drainage density of 0.14 km/km2. Altitudes and slopes vary little and slopes are oriented in most cases towards the southeast (27.34%). Substrate is mostly permeable, which promotes infiltration and aridity of the soil. This contrasts with the Zat basin that is characterized by very variable elevations and slopes, and slopes are mainly exposed to the North and North-West (30.42%), which therefore favors strong runoff and a very high flow velocity. The hydrological contrast observed in the two basins impacts the human use of surface water. These results effectively explain the hydrological behavior and provide managers with useful information for better management and decision-making regarding the two studied hydro systems.

草地灌溉对土壤性质和植物物种组成的影响

草地是欧洲范围内生物物种最为丰富的动植物栖息地之一;为了对大面积的草地开展有效的保护,必须要采取具有针对性和可持续性的管理措施。虽然如今大都已被弃用,但传统上的灌溉却有可能是一种具有可持续性的管理策略。然而,对于一般的湿润性生态区域,人们还不太了解灌溉、土壤特性以及植物物种这3者之间的相互影响。我们旨在将传统的草地灌溉对植物群落的影响从传统的低施肥量效应中分离出来,从而获得植物生态学方面的新知识。我们的考察对象是植物的组成和多样性以及它们与土壤特性(有机态碳、总氮、持水性/保水力、中型土壤动物活力)和土壤养分(无机态氮、磷、钾、镁、硼)指标之间的潜在联系。在田间研究中,我们对过去长期灌溉的13块草地以及未经灌溉的13块草地(其中17块草地经过施肥,9块未经施肥)进行了比较。分析这些草地在一整年时间内的植物多样性和物种组成情况以及土壤养分和土壤特性指标,并且假设不同年份之间的差异不大。研究结果发现,灌溉和施肥使土壤特性和土壤养分发生了改变,但它们对植物物种多样性并无影响,只影响植物的物种组成。淤积土具有更细的粒度,因而拥有更高的保水力和养分储量。因此,需要获取水分和养分资源的禾本科植物在经过灌溉的草地上占据优势。本研究的结果表明,对于中欧地区大量的已开发草地,灌溉不仅能保护其生物多样性,而且还有可能使其植物具有不同的植物功能性状。