The purpose of this project is to assess the downstream effects of damming along the Tigris River in Iraq. Specifically, it will focus on the effects the building of the Mosul Dam in northern Iraq has had on land cover throughout the river basin.
The Mosul Dam is located on the Tigris River, upstream the city of Mosul in Iraq. It has a capacity of 12 billion cubic meters and provides water to a majority of the Ninevah province. The dam started operating on July 7, 1986 for irrigation, floods control, and hydropower generation.
The damming of the Tigris creates issues on both political and environmental levels. As the river crosses international boundaries, upriver damming in one country can affect water resources in another (UN-ESCWA and BGR, 2013). The Tigris is barred by three major dams in Iraq and five in Turkey, thus indirectly giving Turkey some control over the Tigris' characteristics downstream in Iraq. Iraq first dammed the river near Kut in 1939 with subsequent dams built by Samarra (creating Lake Tharthar) in 1954 and in Mosul in 1986. Turkey did not begin building dams until the early 1990s (UN-ESCWA and BGR, 2013).
Damming of rivers can also cause huge environmental consequences. Drastic changes in the riparian and river ecosystems dramatically effect all living organisms of the area. Dams cause erosion due to them holding back sediments that would normally flow downstream to replenish ecosystems. Riverbeds downstream from a dam often are eroded by several meters within a mere few years of first closing a dam. Damming causes changes in temperature, chemical composition, dissolved oxygen, and physical properties to reservoirs that are not fitting for aquatic life and can cause extinction (International Rivers, 2009). Additionally, as dams decrease general river flow, the floodplains downstream have dried out significantly (UN-ESCWA and BGR, 2013). This increases dry particles available to be swept up in duststorms (NOAA, 2009), and may decrease the productivity of successful agriculture.
The Tigris River stems from the mountainous terrain of southeast Turkey, and runs southeast through Iraq before emptying into the Arabian Gulf (NOAA, 2009). The river runs through flat terrain in Iraq, which is largely desert land. South of Baghdad, in central Iraq, large floodplains cover the land until the Tigris meets up with the Euphrates river just north of Al Basrah. While western Iraq is desert, with the exception of the Euphrates River Valley, the Tigris floodplains are more supportive of agriculture and have historically been fertile lands. However in the recent past, 14 dams have been built on the river, impeding the flow of water to the fertile land in southeast Iraq (UN-ESCWA and BGR, 2013).
Climate in Iraq is typical of a desert region, with seasonal heavy rains and long dry summers (NOAA, 2009). The data discussed in this project were taken from May through July months, when precipitation and active weather fronts are rare. Lakes and reservoirs dry out during these months and free up dust particles that, in conjunction with strong Shamal winds, may cause significant dust and sand storms (NOAA, 2009). Continued precipitation and snowmelt in the mountainous regions of Turkey and Iraq may still contribute to river discharge.
In ancient history, the Tigris River Valley largely made up the region home to the civilization of Mesopotamia. Known as the Fertile Crescent, large marshlands were situated in southeast Iraq which housed an extensive freshwater ecosystem and was home to many indigenous peoples. Damming in Iraq began in the 1930s, which was initially done to protect cities such as Baghdad from the dangers of flooding (Issa et al, 2013). Controversies arose in the creation of the dams since populations were displaced and historic landmarks were flooded in order to clear the reservoir (Milner, 2014). In 1990 the Iraqi government began a campaign to intentionally decrease the river discharge to the marshlands through damming (UN-ESCWA and BGR, 2013), which decreased the area of irrigated land by over 10,000 square kilometers (Issa et al, 2013). By 2002, 85% of the marshlands had been destroyed (UN-ESCWA and BGR, 2013). After the fall of the Saddam regime, international efforts have worked to restore the marshlands and by 2006 nearly half of the wetlands had been restored (UN-ESCWA and BGR, 2013). Many agreements between the countries of Turkey, Syria, Iraq and Iran are maintained in order to ensure proper and peaceful use of water resources in the Middle East. Currently, various dams in Iraq, to include those on the Euphrates River, are being used as objects of political power by extremist groups, as it allows them to control power production and water availability for local populations and government (Milner, 2014).
Images from remote sensing reach as far back as the 1970s, giving us the ability to view scenes both before and after building of Tigris River dams. The following images show the Tigris River in Northern Iraq near the city of Mosul in 1977, and then again in 2003, over 25 years after the Mosul Dam was built.
|Figure 1 "Before" and "after" shots of northern Iraq. The NDVI images were created from Landsat MSS and TM data from 1977 and 2002. The image on the left shows the region before the Mosul Dam was built, and the image on the right shows the dam over 25 years after completion. The large reservoir can be seen near the northern edge of the image.|
For the purposes of this project, the Northern Tigris River Basin will be considered to encompass the vicinity of the city of Mosul, the Central Basin in the vicinity of Bayji, and the Southern Basin in the vicinity of Numaniyah.
This project focuses on the Mosul Dam and its effects downstream. Data were downloaded from USGS's Earth Explorer web-based database. Level I data from years before the dam was built were acquired from the Landsat 1-5 MSS archives, and data from after dam completion were downloaded from the Landsat 4-5 TM and Landsat 7 ETM+ SLC-on archives.
The images were processed using Idrisi Selva software. After converting the Landsat Level I images from geotiff into Idrisi format, the images were haze corrected using the SCALAR feature. Each band was corrected so the new minimum value equaled one. Next, each image was cropped to approximately the same gridded area using the WINDOW feature, in order to better compare images from different years and satellites. A Normalized Difference Vegetation Index (NDVI) was made using the red and infrared spectral bands. For images retrieved from early Landsat Multispectral Scanner (MSS) data, bands 5 and 7 were used to create the NDVI. In more recent Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper (ETM+) imagery, bands 3 and 4 were utilized.
The images were also used to produce reclassified images. Using the Cluster function in Idrisi and the red and near infrared bands, the image was reclassified to distribute the land in categories of land use. The land was organized in categories, land covered by water, rural/agriculture, vegetation, and arid land. The area of each of these was found in order to see the change over time.
Before the Mosul Dam was built, vegetated areas in northern Iraq covered approximately 4,200 square kilometers, with the same covering 1,750 and 12,600 square kilometers in the central and southern Tigris River basins respectively. In 1987, soon after the dam became operational, these areas had decreased to 1,600, 1,300, and 3,850 square kilometers. To evaluate long-term effects of the dam, each region was analyzed using data from the turn of the century. In the early 2000s vegetated areas were seen to have increased to 5,725 square kilometers in the northern region, and further decreased to 770 and 2,269 square kilometers in the Central and Southern Tigris River Basins, respectively.
|Figure 2 Reclassified Landsat images from 1977, 1987 and 2002 near the city of Mosul, Iraq.|
|Figure 3 Reclassified Landsat images from 1976, 1987 and 2001 near the city of Bayji, Iraq. Lake Tharthar is seen in the southwest corner of the images.|
|Figure 4 Reclassified Landsat images from 1985, 1987 and 2002 near the city of Numaniyah in southeast Iraq.|
After reviewing our data, we have found the building of the Mosul Dam has had an effect on the surrounding environment. Loss of vegetation has occurred drastically downstream. Areas on the Northern Tigris River Basin have also been affected, though vegetation seems to be increasing in recent years. This is due to the international efforts made to restore the marshlands after the fall of Saddam Hussein. The building of the dam has also led to more dry and arid land, especially in the Central and Southern River Basins.
Issa, I.E., Al-Ansari, N., Sherwany, G., and Knutsson, S., 2013, Sedimentation Processes and Useful Life of Mosul Dam Reservoir, Iraq: Engineering, v. 5, no. 10, p. 779-784.
International Rivers, 2009, Environmental Impacts of Dams: http://www.internationalrivers.org/environmental-impacts-of-dams. [retrieved 3 December 2014]
Milner, A, 2014, Mosul Dam: Why the battle for water matters in Iraq: http://www.bbc.com/news/world-middle-east-28772478. [retrieved 3 December 2014]
National Oceanographic and Atmospheric Association, 2009, Climate of Iraq: http://www.ncdc.noaa.gov/oa/climate/afghan/iraq-narrative.html. [retrieved 3 December 2014]
UN-ESCWA and BGR, 2013, Inventory of Shared Water Resources in Western Asia: Tigris River Basin: http://waterinventory.org/sites/waterinventory.org/files/chapters/Chapter-03-Tigris_River-Basin-web_0.pdf. [retrieved 3 December 2014]
USGS Earth Explorer