پديد آورندگان :
محمدنژاد آروق، وحيد نويسنده استاديار جغرافيا، دانشگاه اروميه , , اصغري سراسكانرود، صياد نويسنده asghari, sayad , گل محمدزاده، بهاالدين نويسنده كارشناس ارشد ژيومورفولوژي،دانشگاه حكيم سبزواري ,
چكيده لاتين :
Introduction
Groundwater is a vital natural resource for the reliable and economic provision of potable water supply in both urban and rural environment. The rapid increase in the human population has increased the use of and demands for groundwater resources for drinking, agricultural, and industrial purposes. And although groundwater is a dynamic and replenishing natural resource, its availability is limited. This is because groundwater occurs in complex subsurface formations, cannot be directly seen on the Earth’s surface, and is a fluctuating resource difficult to measure in both time and space.
Integration of remote sensing data and the geographical information system (GIS) for the exploration of groundwater resources has become a breakthrough in the field of groundwater research, which assists in assessing, monitoring, and conserving groundwater resources. Remote sensing (RS) data is used for qualitative evaluation of groundwater resources by extracting and analyzing geological structures, surface morphology and their hydrologic characteristics. Lithology, topography, stream networks, slope, Precipitation, land use and lineament are factors that affect groundwater potential zones.
The main objective of the present study is to apply innovative approach to assess the groundwater controlling features, to identify And delineate potential groundwater zones and finally build up a groundwater prospect map.
Methodology
The study area lies at the central of west Azarbayjan and in the Urmia district. The district lies between 37?_8´ and 38?_10´ north latitude and 44?_22´ and 45 ? _30´ east longitudes, covering an area of 5191 km2.
GIS, RS and MIF techniques are used for delineation potential groundwater maps. Seven influencing factors, such as lithology, slope, land-use, lineament, drainage, topography, and rainfall have been identified to delineate the groundwater potential zones.
RS data such as Satellite images from ETM+ and SRTM data, geology maps on a scale of 1:100,000 have been used for delineation of thematic layers such as land-use, lithology, lineament, and topography types. Maps of these seven factors are built. Integration of these factors with their potential weights is computed through weighted overlay analysis in ArcGIS. The representative weight of a factor of the potential zone is the sum of all weights from each factor.
Results and Discussion
Slope: The occurrence and movement of groundwater are governed strongly by slope; therefore slope can be considered an important factor in runoff flows and infiltration. The slope map of the study area was prepared based on SRTM data using the spatial analysis tool in ArcGIS 9.3. The slope map ranked in four categories. 0 – 15, 15 - 30, 30 – 45 and > 45. Surface runoff is typically slow in areas of gentle slope, allowing more time for rain water percolation and promotes appreciable groundwater recharge.
Drainage density: Drainage density is defined as the closeness of spacing of stream channels. The drainage density is an inverse function of permeability. The less permeable a rock is, the less the infiltration of rainfall, which conversely tends to be concentrated in surface runoff. Drainage density of the study area is calculated using line density analysis tool in ArcGIS software. High dense network are located in quaternary alluvial depositions.
Lithology and Lineament density: The study area is underlain by Limestone, Dolomite, Crystalline rocks and quaternary alluvial depositions. Alluvium quaternary sediments are spread almost in central and east part of the study area.
Lineaments are structurally controlled linear or curvilinear features, which are identified from the geology maps and satellite image by their relatively linear alignments. These features express the surface topography of the underlying structural features. These factors are hydro-geologically very important as they provide the path ways for groundwater movement. Lineament density of an area can indirectly reveal the groundwater potential, since the presence
of lineaments usually denotes a permeable zone. Areas with high lineament density are good for groundwater potential zones.
Rainfall: The annual average rainfall of the study area is around 341 mm. Rainfall distribution along with the slope gradient directly affects the infiltration rate of runoff water hence increases the possibility of groundwater potential zones. Therefore, iso-precipitation maps have built for study area using spatial analyze tools in ArcGIS.
Delineating the groundwater potential zone: The groundwater potential zones for the study area were generated through the integration of various thematic maps such as., drainage, slope, lithology, topography, lineament, rainfall and land-use using MIF and GIS techniques. The groundwater potential zone of this study area can be divided into four grades, namely very good, good, poor, and very poor. The groundwater potential map demonstrates that the excellent groundwater potential zone is concentrated in the east and north-central region of the study area due to the distribution of alluvial plains and agricultural land with high infiltration ability.
Conclusion
The map of potential ground water zone has built using GIS and MIF techniques in Urmia district. According to the groundwater potential zone map, the very good zones are located in east and north – central of the study area. These classes cover about 2543 km2. These zones have high dense stream network, quaternary alluvial depositions and good agricultural activities. Urmia district is categorized into four different zones, namely ‘very good’, ‘good’, ‘poor’, and ‘very poor’. The results of the present study can serve as guidelines for planning future artificial recharge projects in the study area in order to ensure sustainable groundwater utilization.
This is an empirical method for the exploration of groundwater potential zones using remote sensing and GIS, and it succeeds in proposing potential sites for groundwater zones.
