The climate is mainly of the continental, subtropical semi-arid type, with the north and northeastern mountainous regions having a Mediterranean climate. Rainfall occurs from December to February (or November to April in the mountains) during cool to cold winters, with a day temperature of about 16°C dropping at night to 2°C with a possibility of frost, summers are dry and hot to extremely hot, with a shade temperature of over 43°C during July and August, yet dropping at night to 26°C.

Rainfall is very seasonal and occurs mainly between November and April. Average annual rainfall is estimated at 154 to 200 mm.

Surface water resources

The Tigris is International River originating its source in Turkey. The Tigris river basin in Iraq has a total area of 253000 km², or 54 % of the total river basin area.

Tigris River enters into the Kurdistan Region from 4 km north of Feshkhabuor village in Zakho district extending 44 km of Turkey Syria border, the discharge in the border point is 657 m³/sec. The annual flow is 20.72 billion m³/sec .

Its length from border point to Mosil is 188 km, which 138 km pass through Kurdistan Region.

The average annual runoff as it enters Iraq is estimated at 21.2 km³. All the Tigris tributaries are on its left bank. From upstream to downstream:

•  Pesh-khabour (Fesh-khabour) consists of :

      a- Hizl branch: locates on western part of Zakho district, represents natural boundary of Iraq-Turkey.

      b-Khabour branch: flows from eastern and north-eastern areas  of Zakho city, recharged by some permanents and seasonal streams which are Batoofa, Kokheki, Kani Masi and Amedy streams. The  total length of Khabour is 160 km and it's Annual flow is about 1.96 billion m³ .

   

• The Greater Zab, which originates in Turkey and is partly regulated by the Bakhma dam. It generates 13.18 km³ at its confluence with the Tigris; 62% of the 25 810 km² of river basin is in Iraq;
• The Lesser Zab, which originates in Iran and is equipped with the Dokan dam (6.8 km ). The river basin of 21 475 km² (of which 74% is in Iraqi territory) generates about 7.17 km, of which 5.07 km³ of annual safe yield after the Dokan construction;
• The Al-Adhaim (or Nahr Al Uzaym), which drains about 13 000 km² entirely in Iraq. It generates about 0.79 km³ at its confluence with the Tigris. It is an intermittent stream subject to flash floods;
• The Diyala ( Sirwan) , which originates in Iran and drains about 31 896 km², of which 75% in Iraqi territory. It is equipped with the Darbandikhan dam and generates about 5.74 km³ at its confluence with the Tigris;
• Two other tributaries (the Nahr at Tib, Dewarege (Doveyrich) and Shehabi river, and the Al-Karkha) are outside Kurdistan region

 Groundwater resources

Good quality subterranean water has been found in the foothills of the mountains in the Kurdistan Region and in the area along the right bank of the Euphrates:

• The aquifer in the north-east of the Kurdistan Region has an estimated sustainable discharge of between 10 and 40 m³/s, at depths of five to fifty meters. Its salinity increases towards the south-east of the area, where it reaches 1 mg/1;
• the aquifers on the right bank of the Euphrates river are found at depths up to 300 m, and have an estimated discharge of 13 m³/s. Salinity varies between 0.3 and 0.5 mg/l.

Ground water aquifers in Kurdistan Region consist of extensive alluvial deposits of the Tigris river, and is composed of Mesopotamian and carbonate formations. The alluvial aquifers have limited potential because of poor water quality. The Mesopotamian aquifers in the north-western foothills consist of Fars,  Bakhtiari and alluvial sediments. The Fars formation is made up of anhydrite and gypsum interbedded with limestone, and covers a large area of Iraq. The Bakhtiari and alluvial formations consist of a variety of material, including silt, sand, gravel, conglomerate and boulders, with a thickness of up to 6000 metres. Water quality ranges from 300 to 1000 ppm.

Another major aquifer system is contained in the carbonate layers of the Zagros Mountains. Two main aquifers are found in the limestone and dolomite layers, as well as in the Quaternary alluvium deposits. The limestone aquifer contributes large volumes of water through a number of springs. The alluvial aquifers contain large volume reservoirs, and recharge is estimated at 620 mcm from direct infiltration of rainfall and surface run-off. Water quality is good, ranging from 150 to 1400 ppm.

Irrigation and drainage development

The history of irrigation started 7500 years ago in the land between the Tigris and the Euphrates when the Sumerians built a canal to irrigate wheat and barley.

Irrigation potential was estimated in 1990 at over 2.5 million ha, of which 63% in the Tigris basin. Considering the soil resources, it is estimated that about 2 million hectares are classified as excellent, good or moderately suitable for flood irrigation. With the development of water storage facilities, the regulated flow has increased and changed the irrigation potential significantly. However, irrigation development depends to a large extent on the volume of water released by the upstream countries.

 Institutional environment

The Ministry of Water Resources is in charge of water resources development, irrigation and drainage development, as well as its operation and maintenance. Its major functions are to assess water requirements and resources, control running water, reservoirs, underground water, the construction of dams, canals and drainage systems, soil conservation, classification, land evaluation and use, and research and studies on land and water.

Trends in water resources management

The development of irrigation as it is planned in the upstream countries, particularly the South-east Anatolian (GAP) project in Turkey, and the irrigation projects in Syria will reduce Iraqi irrigation potential unless an agreement is reached on the sharing of waters between the riparian countries. Since water shortages are forecast to occur with the development of irrigation, solutions have to be found for an integrated basin-level planning of water resources development.

Treatment of municipal and industrial wastewater is considered as one way to preserve river water quality. Reuse of treated wastewater for irrigation was also envisaged before 1990. Some industries are already obliged to desalinate the Euphrates waters before using it.