Project-Hydrology

Water measuring stations in the catchment areas of the study area

Water measuring or hydrometric stations are usually established by the Ministry of Energy in different parts of the country and used for surface water studies. According to the existing or future construction plans, measuring the annual amount of water and its quality have different degrees of importance, and the water measuring stations are grade 1, 2, 3, and 4.

The first-class stations are equipped with eschel, cable car bridge and limnograph. Second-class stations have escalators and cable car bridges, third-class stations have escalators and limnographs, and fourth-class stations have only one scale.

Selection of the Reference Period

A statistical period between 1350-1369 and 1399-1400 (a 31-year statistical period) was considered for the hydrological stations. However, it should be noted that the number of wet and dry periods in the statistical period of the existing stations was not considered. In some hydrological stations, the average discharge data was either not available or needed to be corrected for some years in the study period. To address this deficiency and make corrections, the following sources were used:

1- Adjacent stations

2- Update of the comprehensive water balance of the country in the Haleh, Mand, Kel-Mehran, Bandar Abbas-Se Dij and Southern Baluchistan watersheds of the Ministry of Energy (Atlas 90)

3- Report on the update of the water balance of the Southern Baluchistan watershed (between Se Dij and the Pakistan border)

4- Summary report of the review of the first stage and the second stage studies of the Kariani Dam

It is worth mentioning that in the update of the comprehensive water balance of the country in the Haleh, Mand, Kel-Mehran, Bandar Abbas-Se Dij and Southern Baluchistan watersheds of the Ministry of Energy, the trend of discharge data was removed after examining discharge and precipitation data. This data has been used in this report.

 

Surface water (hydrology) of South Balochistan catchment
The South Balochistan watershed includes all the rivers between Sedij and the border of Pakistan and is known by the abbreviated name of "Rabj-Bahuklat".

This watershed is bordered by Hamun Jazmurian watershed and Meshkil watershed from the north, Sedij watershed from the west, Pakistan from the east, and the coast of the Oman Sea from the south.

The length of the common border with the mentioned basins: with the Hamon Jazmurian catchment basin (290 km), with the Meshkil river catchment basin (200 km), with the Sedij river catchment basin (160 km), with the coasts of Oman (350 km).

The area of the mentioned catchment area is 48662 square kilometers, of which 37246 square kilometers are mountains and 11416 square kilometers are plains and foothills.

The cities of Chabahar, Kanarak, Nikshahr, Qasrqand and Sarbaz are located in this basin, and part of the roads from Iranshahr to Chabahar and Saravan are also located in it.

Topography and morphology

The Rabach-Bahuklat catchment area is a mountainous and hilly area, with wide and low-sloping plains in some of its coastal areas.

This basin is limited from the north to the low mountains between the Jazmurian and Meshkil basins, the maximum height of which is 2110 meters.

In the western regions, the heights and hills of Mahors extend to the sea coast, which is drained by a number of seasonal rivers that flow along the north to the south.

Chabahar and Dashtiari plains form the largest flat and low-slope areas of the basin and are flooded when the rivers flood.
 

Hypsometric distribution of sub-basins of South Balochistan (Rabach-Bahuklat)

 

Characteristics of the main rivers of the southern Balochistan watershed
The height of these basins is very low, so that the average height is: 430 meters under Rabach and Kashi basins, 372 meters under Bim Rabach and Bahuklat basins, 605 meters under Bahuklat basins, 980 meters under Nehang-Gishestan basins.

In Bahuklat, this figure decreases to 77%, and under the eastern basin of Bahuklat, about 96% of the area is between 500 and 1500 meters. Due to the runoff regime, the river beds are generally wide and completely eroded. The average slope of the river in Rabach is 4.4 per thousand.In the western basins of Bahuklat, more than 94% of the area has an altitude of less than 1000 meters, but in Bahuklat, this figure decreases to 77%, and under the eastern basin of Bahuklat, about 96% of the area is between 500 and 1500 meters. Due to the runoff regime, the river beds are generally wide and completely eroded. The average slope of the river in Rabach is 4.4 per thousand.

Characteristics of the main rivers of the southern Balochistan watershed
 

Bahuklat river

This river is the most important river in the watershed and consists of a main branch called Sarbaz and a smaller branch called Kajo.

Cashew River is located in the west of Sarbaz and originates from the northern heights of Qasrqand. The major part of its catchment area is formed by low mountain areas and the southern part of this catchment area is formed from horizontal or flat hilly lands and goes under water during floods. In general, most of the flood flows of these rivers spread and evaporate in Bahuklat and Chabahar plains.

Rabech River
This river is located in the western end of the basin and is formed by connecting the sub-branches of Fanuj, Bent, Kanas and Dastgerd. The density of its drainage network is less than other rivers, but its width is greater. The river has a runoff regime.

Kahir River
This river consists of Sarha and Keshik forks and flows along north to south. The major part of its catchment area is made up of mountainous areas and its flow regime is rainy and runoff.

Other rivers
In addition to the mentioned rivers, there are a number of rivers with a small catchment area, which are often the drains of low-altitude, horizontal and low-slope areas adjacent to the Oman Sea.

iver and Jopar River. All these rivers have runoff regime.These rivers from west to east are: Kashi River, Bandini River, Bir River, Sargan RRiver and Jopar River. All these rivers have runoff regime.

In general, it can be said that the runoff of these rivers is prone to accidents. 
 

Correlation equations of annual inundation at the base station and stations with statistical intervals in the South Balochistan watershed

Studying on the river’s water quality
Based on results of chemical analysis of river water samples that are done in water quality measurement stations, the type of anions and cations in the river water are measured and reported.

It is obvious that the water quality of the rivers is primarily dependent on the type of geological formations of the catchment basin and their bed and flow.

And in the second stage, their water quality depends on the underground water drain and the quantity and quality of water returned to the river through natural drains or artificial channels from cultivated lands or industrial areas and residential complexes.

In the South Balochistan watershed, due to the geological formations and the limited expansion of saline formations in the high slopes, the water quality is suitable up to these places, but after the river passes through the deserts and due to the return water from agricultural lands and workshops and drains, this Depending on the river, the water quality of the river becomes more unfavorable and its salts increase.
In general, the investigation of the chemical quality of river water shows that in these basins, the runoff currents, which constitute the majority of surface water resources, have no limit in terms of solute concentration, and only in times of water shortage and only in the downstream stations of Kajo, Rabach rivers, there is a low limit of up to Average is observed especially in terms of absorbable sodium (SAR). Also, with the exception of the Bahu River at the Bahuklat station, the concentration of its water solutes is relatively high. In other rivers, there are no restrictions in terms of agriculture and drinking.
 

Bahoukalat River