مجله سامانه های سطوح آبگیر باران
سال دوم شماره 3 (پیاپی 4، پاییز 1393)

In order to investigate the roles of water harvesting patterns in water saving and increasing rain water productivity under micro catchment water harvesting systems، a field experiment was conducted in East Azarbaijan in the northwest of Iran during 1999-2006. The treatments included two MCWH patterns (small basins and semi-circular bunds)، three catchment sizes (25m2; 49m2 and 81m2)، three runoff area treatments (Natural، cleared and smoothed، wetting and compacting) and two infiltration areas (Natural، soil mixed with polymer at a rate of 1kg/tree) for two new almond varieties. Polymer had no significant effect on water holding. Although the small basin with (9×9)، runoff area compacted and use of polymer gave better results in survival، the growth and productivity of almond، the treatment with small basin (7×7) with compaction and without polymer can be recommended based on an economic analysis. Threshold runoffs were measured to be 2. 5-3. 5، 3. 5-4. 5 and 4. 5-5. 5 mm for natural، cleaned and smoothed، cleaned، wetted and compacted condite، respectively. Seventeen-year (1996-2013) average rainfall is equal to 202 mm، which shows that 84. 4، 65. 3، 51. 3 and 36. 4 of the total precipitation were more than 2، 4، 6 and 8 mm، respectively. Maximum rainfall runoff coefficient for threshold rain of 2، 4، 6 and 8 mm، was obtained to be 0. 57، 0. 35، 0. 22 and 0. 14، respectively. The design runoff coefficient for threshold rain of 2، 4، 6 and 8 mm، was obtained to be 0. 28، 0. 17، 0. 11 and 0. 07، respectively. Determination of threshold runoff has a major role in the success of water harvesting system design.

Determination of threshold runoff is very important since it helps us estimate and design flood and runoff potential، and has an important roleinthe optimal use of precipitation. In this study، rainfall and runoff events were measured in the SanganehKalat watershed during the years 2008 to 2011. Precipitation using a rain gauge and runoff was recorded with five water level gauges four of whichwere installed at the outlet of the sub watershed and one of whichwas installed at the outlet of the main watershed. A total of 128 events were recorded 8 of which generated runoff. According to the defined threshold runoff،some of the precipitation which increases surface soil moisture until runoff is generated، showed that the lowest threshold runoff in the sub watershed is about 1 mm and in the main watershed is about 2. 2 mm. Hence، study of single rainfall event is very important and considering a part of the monthly cumulativeand annual rainfall as runoff is associated with a high error. Runoff volume during the project shows that according to the physiographic factors، soil and vegetation cover of the sub watersheds، the potential of runoff generation is different. Based on the results of this study، according to the area of the sub watershed، the potential of runoff generation in sub watersheds A1 to A4 and S are 116، 11، 26، 28 and 25 cubic meters per hectare per year، respectively.

This research was performed for examining the potential of combining surface and subsurface water harvesting methods in a catchment. For attaining this goal، the present study was done in the Sangane watershed with an area of 600 ha. In the study area، before construction of the underground dam and the recharged dam، in spite of water crisis، a great portion of the subsurface flows and floods were lost from the country without any utilization and a great portion of livestock water for about 12000 sheep was bought at an expensive price. In the study area، water preparation for livestock purposes was performed by a combination of surface and subsurface water harvesting methods. Annually، the combining method suppliesmore than 20000 cubic meters of water with a suitable quality. The supplied water in an earthy dam not only recharges the underground dam; but it is also directly utilized for livestock usages. This research showed that in similar dry and semi-dry areas that were located in the North East of marginal locations of the country، by using this method، a great deal of suitable water for different usages can be supplied and provided.

Currently، much of the water resources in Iran are used in agriculture. As a result، most of the water losses are related to this section. Iran is a developing country and it is located in the arid and semi-aridregions of the world. In these conditions، drought and shortage of water is one of the main challenges in agricultural production. Therefore، development of sustainable agriculture in arid and semi-arid regions depends on the increase in water usage efficiency in these regions. Rainfed agriculture، with 80percent of the earth''s harvested area، yields 62 percent of the food production for the population of the world. Now، the benefits of rainfed agriculture especially in the production of food for a growing world population، is highly considered. Rainfed agriculture has distinct and different characteristics compared to irrigated agriculture and integrated management of water can increase food production by 75 percent and it is an essential step in order to avoid starvation. Due to climatic conditions in Iran and restrictions in water resources and fertile land، providing optimal management and use of water in agriculture can play a key role in food production. Therefore، the rational use of water in agriculture requires proper planning، and new methods of management. And rainwater harvesting are important in this way for rainfed agriculture.

One of the major issue about roof-harvested rainwater is physicochemical and microbiological contaminations of this water and their negative impacts on human health for potable and non-potable usage. Different factors can directly or indirectly affect the quality of roof-harvested rainwater such as: The climate of the region in terms of volume and intensity of rainfall، material and architectural of roof، type and concentration of air pollutants and etc. Extensive studies have been conducted on this subject in different countries although sometimes their target was not to solve the problem of water shortages، but also to help control runoff. In Iran despite the importance of the issue from both perspectives of water supply and flood control، limited studies was performed. Therefore this paper studies the physicochemical and microbiological properties of roof-harvested rainwater and its influencing factors. As well as solutions presents to re-use this water for drinking and non-drinking consumption and finally، recommendations have been proposed according to the different regions of our country.

In most arid and semi-arid regions، because of over-pumping from groundwater and irregular use of river and other reservoirs، planting trees and vegetation cover have been facing difficulties. Therefore، the use of other water resources like rainwater and floodwaters in recent decades has been taken into consideration in these decades. Traditional methods and techniques for water harvesting in most arid and semi-arid regions have been applied for many years، i. e. methods such as rainwater harvesting، floodwater harvesting، fog and dew harvesting، using Qanat and specific wells. Using these methods of water irrigation through microcatchment systems enables us to improve and rehabilitate desert areas and arid and semi-arid regions. This paper will discuss in detail the application of microcatchments for water harvesting for growth of olive trees in the east of the Golestan province. Results of survival of olive planted in microcatchment systems showed t a different significance in one percent level in comparison with general conditions and control. The amount of olive seedlings survival is 100%; but planting olive seedlings in the usual method and without water harvesting system under a water scarcity condition could not be established.

Rainfall is the most variable climatic parameter. These changes occur both in space and time scale which identify the climate of the region. The aim of this study is to evaluate the spatial autocorrelation of precipitation in the Khorasan Razavi province. For this purpose، precipitation data were obtained from12 synoptic stations in Khorasan Razavi. To acquire the variations in seasonal precipitationin Khorasan Razavi، modern statistical methods were applied such as Spatial Autocorrelation، Global Moran''s Index، Local Moran''s I index، Hotspots and cluster analysis (Clusters/Outliers). These methods were applied using Grads، MATLAB and ArcGIS Software Packages. The results showed that rainfall in the Khorasan Razavi province has a high clustering pattern. According to the local Moran index and Hot Spots، rainfall has positive spatial autocorrelation patterns (clusters of high rainfall value) in the central، northwest and northern parts. This pattern of rainfall، at confidence levels of 90%، 95% and 99%، covers totally 25% of the province areas. The southern regions have negative spatial autocorrelation (clusters of low rainfall value) which totally cover an area equal to18 percent of the province. In the other areas of the province which cover 57 percent of the entire area،no significant pattern has been observed. This indicates heterogeneity of rainfall over the province. The present study shows that altitude which is one of the local factors is the most important factor which influences the distribution of rainfall pattern over the province.

Rainwater harvesting (WH) is a technique to supply water for dryland regions. This technique has many sub-divisions with regards to quality and quantity of required water. It is worth mentioning that construction of large dams and withdrawing water from deep wells are not considered as WH methods. Instead، WH is mainly concerned with capturing and utilizing stream flows near the point where it is being generated by rain drops. The present text aims to categorize the WH methods according to the catchment types، collection methods and utilization methods.