MONITORING DESERTIFICATION IN SOME REGIONS OF IRAQ USING GIS TECHNIQUES

Desertification is one of the phenomena that threatening the environmental, economic, and social systems. This study aims to evaluate and monitor desertification in the central parts of Iraq between the Tigris and Euphrates rivers through the use of remote sensing techniques and geographic information systems. The Normalized difference vegetation index NDVI and the crust index CI were used, which were applied to two of the Landsat ETM + and OLI satellite imagery during the years 1990 and 2019. The research results showed that the total area of the vegetation cover was 2620 km 2 in 1990, while there was a marked decrease in the area Vegetation cover 764 km 2 in 2019, accounting for 34.8% (medium desertification) and 10.2% (high desertification), respectively. Also, the results showed that sand dunes occupied an area of 767 km 2 in 1990, while the area of sand dunes increased to 1723 km 2 in 2019, with a rate of 10.2% )medium desertification ( and 22.9% (severe desertification), respectively. It was noted that the overall rate of decrease in vegetation cover was 21.33 km 2 year -1 while the overall rate of increase in ground erosion in the area is 10.99 km 2 year -1 . Keyword: desertification, monitoring, landsat, remote sensing, GIS ةيقارعلا ةيعارزلا مولعلا ةلجم 2021 : 52 ) 3 :) 620 625 يميمتلا ةيفا رغجلا تامولعملا مظن تاينقت مادختساب قا رعلا قطانم ضعب يف رحصتلا ةبقا رم يميمتلا مظاك نيساي دعاسم ذاتسا مسق مولع وجلا – ةيلك مولعلا ةعماجلا ةيرصنتسملا صلختسملا ةبقا رمو مييقت ىلا ةساردلا هذه فدهت ,يعامتجلااو يداصتقلااو يئيبلا ماظنلا ددهت يتلا رهاوظلا نم رحصتلا ةرهاظ دعت دعب نع راعشتسلاا تاينقت مادختسا للاخ نم تا رفلاو ةلجد يرهن نيب ةعقاولاو قا رعلا نم ىطسولا ءا زجلاا يف رحصتلا شؤم مادختسا مت .ةيفا رغجلا تامولعملا مظنو يتابنلا ءاطغلا ر NDVI ةرشقلا رشؤمو CI روص نم نينثلا تقبط يتلاو تاسدنلا يعانصلا رمقلا ETM+ و OLI تاونسلا للاخ 1990 و 2019 ثحبلا جئاتن ترهظا . ةيلكلا ةحاسملا نا تناك يتابنلا ءاطغلل 2620 ماع يف عبرم رتم وليك 1990 اطغلا ةحاسم يف ضوحلم ناصقن كانه ناك امنيب , ء يتابنلا 764 ماع يف رتم وليك 2019 هتبسن امب 34.8 % طسوتم رحصت ( ) و 10.2 % )يلاع رحصت( ةحاسملا نم ,ةساردلا ةقطنمل ةيلكلا يا.يلاوتلا ىلع ةحاسم تلغش ةيلمرلا نابثكلا نا جئاتنلا ترهظا اًض 767 عبرم رتم وليك ماع يف 1990 ىلا ةيلمرلا نابثكلا ةحاسم تدادزا امنيب , 1723 ماع يف عبرم رتم وليك 2019 هتبسن امب 34 . 10.2 % و )طسوتم رحصت( 22.9 .يلاوتلا ىلع ,ةسا ردلا ةقطنمل ةيلكلا ةحاسملا نم ) ديدش رحصت( % ماعلا لدعملا نا ظحول وه يتابنلا ءاطغلا ناصقنل 21.33 ةنس /عبرم رتموليك ، وه ةقطنملا يق يضرلاا فا رجنلاا ةدايزل ماعلا لدعملا امنيب 10.99 .ةنس/عبرم رتم وليك ةيحاتفملا تاملكلا : رحصتلا ، ةبقا رملا ، تاسدنلا ، يئانلا سسحتلا ، ةيفا رغجلا تامولعملا مظن . Received:11/5/2020, Accepted:18/8/2020 Iraqi Journal of Agricultural Sciences –2021:52(3):620-625 Al-Timimi 62


INTRODUCTION
The international community has become aware of the desertification problem and has taken action towards it. In 1977, during the United Nations Conference on Desertification (UNCOD) in Nairobi, Kenya, the desertification problem was discussed as an issue worldwide for the first time, and an Action Plan to Combat Desertification (PACD) was prepared. In 1992, at the United Nations Conference on Environment and Development (UNCOD) held in Rio de Janeiro, Brazil, both the Earth Summit and Agenda 21 called on the United Nations General Assembly to form a committee of member governments to prepare an integrated legal mechanism to address the problem of desertification. Desertification means land degradation in arid and semi-arid regions and in dry and sub-humid areas that results from various factors, including climate changes and human activities (3), (16), (18). This does not mean closing the debate to develop the definition, as it is proposed at the level of the United Nations and the competent authorities, and this is due to the fact that the study of desertification is relatively new as the first scientific text bearing this designation appeared about 50 years ago. The first map of desertification was completed by the subsidiary bodies of the United Nations was In 1977, this coincided with the convening of the United Nations Desertification Conference in Nairobi, Kenya (13), (17). In fact, desertification is the process of destroying or destroying the vital energy of the earth, which can eventually lead to conditions similar to desert conditions, which is a manifestation of the widespread deterioration of the ecosystems that leads to the shrinking of the vital energy of the earth represented in plant and animal production and from there the effect in sustaining human existence. There are many stages in the desertification process, but whatever their form, the final stage will be complete desert with vital productivity reaching zero.Iraq lies in the arid and semiarid region is exposed to desertification problems, especially in the middle and southern parts of Iraq, which are estimated to be about one million hectares (8),(19). Desertification phenomenon is considered one of the dangerous international environmental phenomena, becouse its effects are not confined to certain places, rather they generally cover large areas of the world, and particularly in the dry and semi-dry environments, besides the semi-wet areas. The causes of desertification in the Iraq have been identified as meteorological, pedological, geological and agricultural problems. Losses in soil fertility , movement of the desert environment, population migration, and great losses in human and material resources are the main outcome (21). Many researchers have studied this phenomenon such as, Ayad and Wuhan studied the monitoring desertification in Shaanxi province, China. The results showed that the study area has severe desertification with desertification area accounting for 88.9% of the whole area in 1999 (6). Hadeel and others studied the sensitivity of desertification in Basrah city, the results revealed that the severe desertification were located in the western southern parts of the region (7). Pashaei and others studied the desertification Vulnerability Index in Iran, the results showed that about 22% or the study area was classified as medium vulnerability of desertification, while 60% were classified as highly vulnerable to desertification. (15). Abdul Razzak and othes used the remote sensing data in Karbala Governorate, the results reveal that the region of study has severe desertification because the area has suffered from erosion, urban growth, and poverty of water resources (20). Dulliami studied the Monitoring of desertification in the Baiji region, the results reached the prevalence of degrees of severe and very severe deterioration in sand dunes, while degrees of low and moderate deterioration were relatively less (5). The aim of this study is to evaluate and monitor desertification in the central parts of Iraq between the Tigris and Euphrates rivers through the use of remote sensing techniques and geographic information systems, using vegetation index and the CI crust index.

MATERIALS AND METHODS Study area
Iraq is a large Mesopotamian alluvial plain, Consisting of the Tigris and the Euphrates rivers (11). The study area is lie between the Tigris and the Euphrates rivers, in Wasit and Babel governorates, which includes the Al-Suwaira, Al-Mahawil , and Al-Musayab district. It is located in the sedimentary plain in Iraq. The study area was chosen because the region contains agricultural lands on both sides of the Two Rivers, which is one of the agricultural fertile lands in Iraq. see Figure1.

Figure 1. map of the study areas location
Iraq can be dividied into three climatic regions depending on the rainfall parameter : Arid and Semi-Arid Zone where annual rainfall above 400 mm, Steppes Zone where annual precipitation of 200-400 mm, and Desert Zone where annual rainfall less than 200 mm, the spatial distribution of annual mean rainfall in the study area ranges between 50-100 mm (9). The temperature reaches the highest value for the months of August and July and reached 36 C, and the lowest value in January and December and reached 9 o C , in the study area the mean temperature ranges between (20-25) o C (11).The mean annual of wind speed was range from 3.5-4.5 m/sec (1). The two images of Landsat which her Path was 168 and Row was 37 have been downloaded from the U.S. Geological Survey server. The first image was Landsat 5 thematic mapper acquired on April 1990, while the second image was Landsat 8 the operational land imager OLI required on April 2019 for a period of 29 years (1990-2019). The preprocessing of the images included geometric corrections. The two Landsat images were projection UTM zone N 38. All indices are derived from the Landsat satellite imagery downloaded from the USGS website (www.earthexplorer.com). The two images of Landsat which her Path was 168 and Row was 37 have been used in this study and downloaded from the U.S. Geological Survey server. The first image was Landsat 5 thematic mapper acquired on 24 April 1990, while the second image was Landsat 8 the operational land imager OLI required on 21 March 2019 for a period of 29 years (1990-2019). The preprocessing of the images included geometric corrections. The two Landsat images were projection UTM zone N 38. All indices are derived from the Landsat satellite imagery downloaded from the USGS website (www.earthexplorer.com). These indicators are:

The Normalized difference vegetation index (NDVI)
The Normalized difference vegetation index, known as NDVI, is one of the most widely used spectral indicators in the field of satellite image analysis, vegetation study, fire and desertification, and other natural phenomena . NDVI can be defiend as a ratio between the red (R) and near-infrared (NIR) values (14);

NDVI = NIR − RED NIR + RED Crust Index (CI)
Crust Index, known as CI, is used to recognize the soil having sand deposition. Soil having sand deposition will appear dark as compared to the other soil types due the absence of organic matter in it. This index can be used on any satellite imagery having Blue (400-500 nm) and Red (500-600 nm) band. The value of CI ranges from 0 to +2.This guide represents the difference between the third and first bundles on their sum subtracted from one. As it is the highest in the first package, and it is characterized by monitoring the thin layer that forms on the surface of the soil or sand dunes, and hence is considered one of the important indicators in expressing the movement and activity of sand dunes(10). The form of spectral crust index can be given by: Crust index and NDVI algorithms were applied to images. The vegetation cover, drifting sand images were interpreted and statistically analyzed to produce desertification severity maps based on the vegetation cover and extent of drifting sand.

RESULTS AND DISCUSSION
Normalized Difference Vegetation Index (NDVI) and Crust Index (CI) were derived from Landsat images for the years 1990 and 2019. Figure 2 A and B, illustrate the map of vegetation cover derived from NDVI index over the study area between 1990 and 2019, while Table 2, reveals the related statistics which include, the amount of area for each region, the percentage of all regions. The NDVI results showed that in Al-Suwaira and Al-Mahawil district were the biggest decline by 30.57% and 27.74% in the vegetation cover area. covering 34.8% of the area, vegetation cover is designated as a medium degraded land in 1990, while it decreased to 10.2% in the year 2019 and designated as high degraded land. Desertification (vegetation degradation) was at a medium level in Al-Suwaira in1990, while it was at a high level in 2019. In Al-Mahawil, desertification was at a medium level in 1990, while it rose tohigh level in 2019. The high level has dominated Al-Musayab city during the study period.

Figure 2. A Sand drifting of the study area in 1990, B Sand drifting of the study area in 2019
The sand drifting derived from CI index showed that Al-Suwaira has the biggest increase by 32%, while Al-Musayab has 17.03% in the sand drifting.Desertification (sand drifting degradation) was at a medium level in Al-Suwaira and Al-Musayab district in1990, while it was at a high level in 2019. In Al-Mahawil, desertification was at a low level in 1990, while it rose to medium level in 2019.

CONCLUSION
Using Remote sensing and GIS techniques are very necessary for managing the natural resources. In this study, the thematic Mapper (TM), and Operational Land Imager (OLI) images have been used for the detection of desertification changes. In this study, the trend of desertification was increasing during the period. The results of NDVI revealed that total vegetation cover was 2620 km2 in the year 1990, while it decreased to 764 km2 in the year 2019. The desertified areas accounting for 24 % of the total area, while the overall average of the vegetation cover decrease rate 21.33 km 2 year −1 . The drifting sand coverage had rather extended toward the cultivated lands areas. the drifting sand areas in 2019 are larger than those in 1990. The overall average of the land drifting increase rate in the study area was 10.99 km 2 year −1 . The decrease in vegetation cover can be attributed to the poverty of irrigation water and water resources during droughts, as well as the massive urban sprawl in the study area and the surrounding provinces. The decrease in vegetation cover in the studied area is due to the decrease in the amount of rain during the study period. Then, the decrease in rainfall amounts led to a significant decrease in the surface and groundwater resources of the study area such as rivers, lakes and groundwater, and thus the soil moisture content.