Makran-Watersheds

Information on Watersheds of the Study Area

In terms of groundwater studies, the Makran region is most consistent with the South Balochistan watershed (one of the 30 main watersheds in the country). The South Balochistan watershed has 15 study areas. According to available statistics, only 51 piezometers have been drilled in 4 study areas of this basin.

The boundaries of the South Balochistan watershed are like a parallelogram, with one of its long sides located north of the Makran mountain range and the other on the southern coast of the Oman Sea. The two smaller sides of this basin are one in the east, part of the border of Iran with Pakistan, and the other in the west, the border of this basin with the Bandar Abbas-Sidiq basin.

The plains of the basin are mainly spread along the valleys formed by surface flows, with a general direction from the mountains (north) to the sea (south). The plains located on the coast of the Oman Sea have a slight slope, and often rivers enter these plains and coastal plains at their lower reaches, and then flow into the Oman Sea.

The plains formed in the mountainous areas of the basin follow the pattern of folding, tectonics, large and small faults, and some of them are located along the folds and fault lines.

In general, the plains of the South Balochistan basin can be classified into two categories based on their shape and distribution:

1. The first category consists of plains that have formed in the northern and mountainous regions, along the margins of large rivers and streams.

2. The second category consists of plains that are located along the coast of the Oman Sea in the form of vast expanses parallel to the coast.

The plains in the mountainous areas are generally limited in area, have a low thickness of alluvial deposits, and are mainly coarse-grained.

Usually, between 2 and 5 floods with different intensities occur annually in southern Balochistan, depending on the amount of rainfall, and generally in the summer.

The maximum water discharge time of a river caused by these floods is 24 hours, and the river is dry for the rest of the time. The peak discharge of a river occurs about 3 to 9 hours after the rainfall. Therefore, the rivers in the region only have water during the flood season.

There are several small rivers with low water discharge in this region that are fed by springs and are used for drinking and agriculture by the local population.
 

The South Baluchistan watershed is located in the southern part of Sistan and Baluchestan province. It is bordered by the Basaghard heights and the Jazmurian and Mashkil watersheds to the north, the Oman Sea to the south, the Pakistan-Iran border to the east, and Hormozgan province to the west. This basin includes several sub-basins: Shani Khor in the northeast, the Bahu Kalat River sub-basin, the Nikshahr and Kahrir sub-basin, Sargaz and Chabahar, Bandasin, and the Rabch sub-basin.

It consists of two parts: mountainous and plain. The most important rivers in this basin from east to west are: Shani Khor River, Sarbaz, Kajoo, which after passing through the mountainous areas of Sarbaz and Qaleh Qand in the Dashtiari region, merge to form the Bahu Kalat River.

The South Baluchistan watershed is separated from the Jazmurian and Mashkil watersheds in Sistan and Baluchestan province by the Basaghard heights. The general direction of the rivers in this basin is from north to south, and they eventually discharge into the Oman Sea.

The Nikshahr and Kahrir rivers also flow from north to south and discharge into the Oman Sea. The mountainous part is called Nikshahr and the flat part is called Kahrir.

In the middle of these two rivers, smaller rivers such as Shi Kolak, Gargaru, Nalint, Lndsharqi, Lnd Gharbi, and Zener originate from the middle heights and discharge into the flat lands of Pir Sohrab and Dashtiari.

In terms of political divisions, this basin is located within the Sarbaz, Chabahar, Nikshahr, and Konarak counties. The northern part of this basin is mountainous, and agricultural activities are mainly carried out on the terraces along the river in small and narrow plots in the direction of the river. The most important areas are Sarbaz, Rask, Qasr Qand, Nikshahr, Fanuj, and Bent and Hangam.

In the plain part of this basin, the most important agricultural areas include the Pishin, Bahu Kalat, Pir Sohrab, and Avarki plains and the Lash (Zarabad) plain.

The most important river in the western part of this basin is the Rabch (Kariani) River, which originates from the Fanuj heights and after passing through the Bent region and joining the tributaries in the Bent and Hangam region, enters the Zarabad (Lash) plain. After feeding the groundwater table of this plain, it connects to the Oman Sea.

In the middle of the Kahrir and Bahu Kalat river basin, several small watercourses originate from the heights south of Pir Sohrab and after passing through the Chabahar, Sargaz, and Konarak regions, they also discharge into the Oman Sea.