پديد آورندگان :
طالبي حسين‌آباد، فاطمه نويسنده كارشناس ارشد هواشناسي كشاورزي، دانشگاه فردوسي مشهد Talebi Hossein Abad, Fateme , شاهدي، مهري نويسنده كارشناس ارشد هواشناسي كشاورزي، دانشگاه فردوسي مشهد Shahedi, Mehri , ولايتي، سعدالله نويسنده استاد زمين شناسي، دانشگاه فردوسي مشهد Velaayati, Sadollah , داوري، كامران نويسنده دانشيار گروه مهندسي آب دانشكده كشاورزي، دانشگاه فردوسي مشهد Davary, Kamran
كليدواژه :
Kashaf Rud basin , Water resources budget , Renewable water , بيلان منابع آب , آب برگشتي , حوضه آبريز كشف رود , آب تجديد پذير , Groundwater depletion
چكيده لاتين :
1. INTRODUCTION
In the adoption of a sustainable development approach to water resources of a region, the quantification of renewable resources is of paramount importance. An important step to ensure the sustainability and estimate renewable water is the accurate calculation of basin water budget. In aquifers with excessive appropriation, a comprehensive, accurate and reliable estimate of groundwater budget is essential. Computer models and available methods require extensive information to establish an appropriate budget equation and estimate renewable water in the basin. Since such information is not readily available, these models are generally not practical. In addition, these models are mainly suitable for small spatial and temporal scales. Given the lack of information and data, attempts have been made to devise a method for improving water budget instructions of the Department of Energy so that it can be used in applied studies.
2. THEORETICAL FRAMEWORK
Renewable and non-renewable water resources: In computing water resources in a basis, a distinction is made between renewable and non-renewable water resources. The latter is groundwater bodies (deep aquifers) that have a negligible rate of recharge on human time-scale. The former is the amount of water that can be restored during the annual cycle by the basis. All of this is not accessible for consumption. According to FAO definition, exploitable water resources (manageable water resources or water development potential) are associated with factors such as the economic and environmental feasibility of storing floodwater behind dams or extracting groundwater; the possibility of absorbing (consumption and charging) water which naturally flows in the basin before the outflow, and the release of minimum flow required for downstream (water rights, water quality, sustainability, environmental requirements). In the present study, the difference between "input from adjacent basins" and "output to the adjacent basin" is considered in the calculation of the renewable water at the basin scale. In fact, the part of the renewable water that (for above-mentionedreasons ) is not exploitable appears in the output. Of course, if a certain contribution should be assigned for the downstream release (which is not met under current conditions), it is necessary to include the actual amount of renewable water (exploitable) in calculations. The actual renewable water after establishing sub-basin water budget is calculated according to the following relations:
RW = (R+I)+(Ri+Gi)-(Ro+Go)
In the above equation, RW is the renewable water, I and R respectively represent the volume of water infiltration and surface runoff caused by the rain, Ri and Ro are the input and output runoff and Gi and Go are input and output underground streams.
RW = (R+I)+(Ri+Gi)-(Ro+Go)
3. METHODOLOGY
To estimate the vlaues of water budget components, some initiatives need to be taken. Also, these initiatives should be adopted at a limited scale to obtain optimal results in terms of physical reality and available data. To do so, some rules and assumptions were considered to estimate the values of the components of the water budget. Moreover, the opinions of experts (experts and professors who were familiar with local conditions and resources) were used. In this study, water budget components in the Kashafrud sub-basins were estimated by optimizaiton through trial and error with the aim of minimizing water balance. In the final stage, with a combination of upstream and downstream in each sub-basin, water budget is controlled. Then, the concept of renewable water and its estimation is addressed.
4. DISCUSSION
The average annual rainfall in the Kashaf Rud Basin (an area of 16751 km2) is about 4318 mcm which due to the dry climate, about 77% of it (3330 mcm) has become inaccessible through evaporation and transpiration as soil moisture storage (green water). Only 988 mcm of annual precipitation remain in the hydrological cycle, which is called natural renewable water. The maximum and minimum amount of actual renewable water are respectively 1222 and 545 mcm. In fact, the average renewable water of Kashaf Rud Basin is equivalent to 884 mcm. This volume of water can be seen as the main asset of this basin in the long term, out of which about 609 mcm recharge groundwater aquifers (RWg). A comparison of water resources and renewable water indicates that even in the wet years, water resources appropriation is greater than renewable water.
5. CONCLUSION & SUGGESTIONS
Given the lack of information and the impossibility of measuring some components of the water budget, experts’ opinions were sought to balance water resources budget without any predefined framework. For this reason, there were diverse and sometimes conflicting results in establishing the balance. To prevent this, a clear definition of “the expert” was needed. According to our definition, experts are people who have gained specialized knowledge, experience and pertinent understanding through field visits and different types of data in every region over time. In this research, experts’ opinions on the reliability of the information, physical relationship governing basins, and basin comparisons in different geographic areas were sought. In fact, gaining a proper understanding of the relationship between parameters in areas that lack adequate and valid data, the proper optimization through physical, geographical and climatic constraints is only possible when the accuracy of the various stages from constraints and assumptions to results of each parameter and comparison of basins (under different geographic and climatic conditions) are confirmed by experts. This study is hoped to lay the groundwork for the proper application of experts’ empirical knowledge to achieve a reasonable estimate of the water balance.
