جستجوی مقالات مرتبط با کلیدواژه "کم آبی" در نشریات گروه "محیط زیست"

Increasing urbanization has a profound effect on the ecological structures. One of the most important challenges is water shortage. Concurrently, urban green space is major water consuming. The green space dependence on groundwater and drinking water in Iran has led to a decline in groundwater levels and increasing water demand. While, cities embrace impervious surface which not only create run off, but also it determinate recharge and flood in rainy seasons. Mohajeran is one of those cities facing with these problems. It seems that water sensitive urban design (WSUD), beside ecological design frameworks are able to represent appropriate solution. In this study First, the sources and uses of water is identified on basis of water sensitive design then, the strategies for green spaces development in the city of Mohajeran is presented. The results indicated that potable water resources (Runoff, rain and grey water) have a considerable potential to substitution with groundwater resources in watering the green spaces. Therefore, development strategies were proposed to develop drought resilient green space on basis of the best management practices such as urban runoff management, rainwater harvest in residential houses, sewage treatment. Today, cities face a variety of challenges, but also complex, which is called as wicked problems. Climate change with increasing frequency and severity of rainfall, long periods of heat and drought, urban population growth and its consequences, water crisis and its supply challenges, environmental pollution in all its dimensions, and extensive changes in land use are among these issues. Meanwhile, the interaction of climate change, water and urban environments, and the challenges it poses, is a challenging part of the issue. There are different approaches to integrate managing water resources in urban areas. This theme was titled "Integrated drinking water management" between 1960 and 1970 by the Civil Engineering Society. This topic has been introduced as “low impact development” in the United States, “sustainable drainage system” in the UK, water sensitive urban design in Australia and New Zealand, “the sponge cities” in the Netherlands, or generally known as the Green-Blue Infrastructure. Australia is antecedent in developing of water sensitive urban design (WSUD) approach due to climate change and drought. WSUD is based on decentralizing approach in water resources management which focuses on a local Practice. Its purpose is to Plan and design of urban fabric to manages and protect natural water cycles in the urban environment in a way that ensures the sensitivity of water management to hydrological, natural and ecological processes. This approach seeks to manage two contradictory problems of flood / runoff and water stress which caused by drought. For this reason, it tries to conceive the cycle of water as a multi-layered system and, avoiding isolated and fragmented approaches, manage water system in the artificial environment and ecosystem appropriately. WSUD Approach includes two key dimensions: the first dimension is water sensitivity consideration and design is the second dimension. In the first dimension, the integrity of water management in the urban environment is considered. While, the planning and design landscape in related to the management of water resources is addressed. In hydrology the concept of ecological design is well defined by Water Sensitive Urban Design (WSUD). Ecological design could be considered alongside of WSUD in landscape design which is any form of design that minimizes environmentally destructive impacts by integrating itself with living processes. Nowadays, more than 500 cities in Iran face with water shortage problems. Mohajeran city is one of them which is the subject of this study. This city suffer difficulty emitting runoff during rainy season and suffers from drought in dry season. It seems that the best manner to curb these problems is following WUCD principles and employing ecological principles concurrently. . Mohajeran city is located at the West of part of Markazi province. Mohajeran's climate is semi dry. The average precipitation of this region is 337 mm rain annually. The city is about 1600 hectares. Total green spaces area is about 160 hectares. Figure 1 shows the location of Mohajeran on the map of Iran, and indicates the study area in Mohajeran which is an urban residential district with an area of 0.19 km2. Fig. 1 Location of the study area in Mohajeran, Iran At first this article reviews WSUD literature related to water shortage conditions, collecting rain water, reusing of gray water in urban landscapes, promoting water consumption efficiency, then applies ecological principle to create an strategic plan to promoting urban landscape. The second part of research was conducted based on ecological design principles that expressed by Van der Ryn and Cowan in 1996. At first a review of WSUD literature related to water shortage conditions, collecting rain water, reusing of gray water in urban landscapes, promoting water consumption efficiency and ecological was carried out. Then we tried to use the ecological design and WSUD concepts in order to design more effective green landscape. To achieve this goal the exact volume of rainwater had to be estimated. So equation1 was used: (1) Where Q [m3] is the annual volume of collect able rainwater; Ca is the average runoff coefficient; S is the seasonal loss coefficient (the ratio of rainfall in rainy season to annual rainfall); I is the initial split-flow coefficient (the ratio of rainfall rejecting first flush to annual rainfall); A [m2] is the rainwater harvesting area; H [mm] is the rainfall with different occurrence probabilities; Ca was estimated by using Eqs. (2) (2) Where Ci is the runoff coefficient of different underlying surfaces; Ai [m2] is the areas of different underlying surfaces It is believed that runoff is a precious resource and should have been used in Mohajeran city but unfortunately has been neglected and many problems such as inundation and flooding and water shortage in dry seasons have roots in ignoring it. Therefore, runoff must be stored and reused. To calculate cisterns which have capability to store water in rainy season and use it during dry season we use equation 3: Cistern capacity can be estimated by using Eq4 (3) Where Ca is the runoff coefficient of different underlying surfaces; Ai [m2] is the areas of different underlying surfaces and h [mm] is the rainfall with different occurrence probabilities Another uncommon water resource in Mohajeran city is grey water. Passing some stages of purification will help it to be reused in landscape irrigation Annual precipitation in the study area is 337 mm so by use of equation 1 the volume of the collectible water is 4021.7 m3 annually. The Maximum volume of runoff is for Rooftops and pavement areathe minimum amount of runoff. Figure 3 shows volume of collectible water in different land uses in the study area.

Water shortage is a crucial challenge that threatens future of landscape development in Iran. Naturally it intensifies by climate change that will be led to water stress of ecosystems. The water stress have confronted universities campus landscape with serious challenges especially those that located in arid and semi-arid areas such as center of Iran. Malayer University has had serious challenges due to water shortage in green space development in spite of fast growth. Local adaptation and mitigation actions have a high priority in dry context. Successful adaptation and mitigation need to increase ecological resilience and provide appropriate water resources without threaten the other places and species to meet their needs. Adoption strategies emphasis on ecological resilience and mitigation strategy stress on not only improvement of ecological function against climate change but also reduction the intensifying climate change factors such as greenhouse gases(GHG). Thus ecological resilience improvement will assist the continuum of ecosystems functions and will support mitigation movements. Therefore it is an essential and vital role of planning to cope with wicked problems due to climate changes. Climate change has faced our society with complex problems simultaneously increasing uncertainty. Resilience is an ideal option in access to cope uncertainty that try to recover systems from disruption. As Friend &Moench(2013) pointed the goals of develop is resilience or “an aspect of what development is”. But resilience here defined as ability of absorb shocks and increasing system ability to cope with challenges and conserve the system integrity and sustainably, although may it pass from one situation to new once. It does not mean as bouncing back the system. The emphasis is on sustainability continuum of ecological structure and functions. Although system could be experience some changes. Iran has experienced great dryness challenges. Thereupon water shortage change into an ongoing threat of a dry country and it is a sign of wide spread crises through the country in near future. Malayer University that founded in 2005 has been developed rapidly. It tackled with water limitations for all kind of uses. Water limitation is a main obstacle in green landscape design of university campus too. The article tried to review resilience concept in water shortage conditions and present solutions for water deficit by rain harvest and reuse of gray water in campus landscape design from one side and increase water use efficiency by wise and ecological planting and reduce the water needs by selection of planet species with low water requirement from another side. Method and materials: University of Malayer located at county as same name (Malayer) and in North West of Hamadan province. The area has a semi dry climate. The area receives about 300 mm rain annually in average. The average of minimum temperature is -4 and the average of maximum temperature is 34.7 degree of centigrade. Total area of campus is about 55 hectare that has been built in 2005.Total built area is about 46000 square meters up to now. Slope of campus fluctuate between 3 to 7 percent. 70 percent of 55 hectares is in cult. Soil tests indicated the presence of clay soils in combination with organic materials. The soil salinity is low and without restrictions. The existing vegetation cover can be divided into two categories: 1-Herbaceousspecies, mainly in under developed parts of campus, Characteristics of those species are: wild plant, seasonal growth and short growing period. Plants are drying by beginning of warm season and increase water stress. These plants include species such as: Peganumharmala, Achilleamillefolium, Descurainia Sophia, Gundeliatournefortii and Fritillaria sp. 2-plantingtrees and shrubs that include limit species such as: black pine, cedar and cypress, sycamore, mulberry, willow usual, walnuts, grapes, Cotoneasternummularia, Crataegusaronia, differenttypes of roses, lavender, Rosemary. The main problems of campus green space are: Planting sensitive vegetable to drought, water resources shortage and low efficiency in water irrigation systems. This research has been done based on ecological design principles that expressed by Van der Ryn and Cowan in 1996. The study tries to use the ecological resilience based on global warming trend and water shortage in order to design more effective green landscape. This section includes four steps: 1- Analyses of water resources in campus 2- Analyses of water irrigation efficiency 3- Analyses of plane species resilience against water shortage, ecological diversity and diversity in ecological functions. The result shows area could store about 19000 cubic meters water from rain annually. This volume is enough to irrigation of green space during the year. Moreover harvest runoff is possible from pedestrians and streets. We could access to 90000 cubic meters water by construction of primary waste water treatment systems. In addition change of traditional irrigation system is necessary that will increase irrigation efficiency. Meanwhile mulching can reduce surface evaporation and decrease water needs. Main and dominant plant species flexibility has been analyzed based on Hunter Model (2008). As a result vulnerable species identified, from anther hand new and native species was chose. The native species were selected that have following characteristics: Resistance against water stress, adopted by ecosystem conditions, diversity in ecological function, quality of growth and reproductive and less water requirement. Finally campus landscape has been design based on rain harvest and reuse of gray water (Fig. 1). Conclusion; Landscape design is an alternative and additional tool for climate change and global warming. Landscape design could apply ecological principles in order to cope with climate change threats especially in dry regions. Campus landscapes of Malayer as sample chose to examine ability of ecological design. The result showed, green space of campus could be developed by utilize of potential water resources. Campus landscape could be improved by wise selection of planning species. The species should be resistance against water stress and climate changes. As result ecosystem service will be improved by wise develop of campus landscape through ecological design principles. Is this experiment applicable in more complicated places such as urban landscape? Simultaneously other approaches such as carbon sequestration are applicable? These two questions are new subjects for further practical research especially in the arid areas that faced with climate changes threats.