Rechna Doab Benchmark Basin

Size: The gross area of the Doab is 2.97 million hectares,including 2.3 million hectares of cultivable land. It has a maximum length of 403 km and maximum width of 113 km.

Location: The Rechna Doab is located between the Chenab and Ravi Rivers. It lies between longitude 71^o 48' to 75^o 20' East and latitude 30^o 31' to 32^o 51' North. It is one of the oldest and most intensively developed irrigated areas of the Punjab Province of Pakistan.

Figure 1 : Location of Rechna Doab

Climate:

The area is subtropical, continental lowland, designated as semi-arid. The climate is characterized by large seasonal fluctuation of temperature and rainfall. Summers are long and hot, lasting from April through September with temperatures ranging from 21^oC to 49^oC. The winter season lasts from December through February; temperatures ranging between 25^oC to 27^oC.

Mean annual precipitation is about 650 mm in the Upper Rechna, and 375 mm in the Central and Lower Rechna Doab. Nearly 75 percent of the annual rainfall occurs during the monsoon season lasting from mid-June to mid-September.

Aquifer:

Much of the basin is underlain by saline groundwater with bands of sweet water near the two rivers.

Soil and Topography:

Alluvial deposits transported by the Indus and its tributaries form the Rechna Doab. The soils are predominantly medium textured to moderately coarse with favorable permeability characteristics .The soils are generally low in organic matter and are adaptable to wide variety of crops. Soil pH is generally basic, in the range of 8 to 8.5.

The topography of the Rechna Doab is relatively flat with land surface gradient ranging from about 0.25 m per km. in the north and northeast to less than 0.2 m per km towards the south and southwest down the Doab.

Figure 4 : Surface Elevation

Irrigation System:

Due to scanty rainfall as well as its unfavorable seasonal distribution, agriculture is not possible without irrigation in Rechna Doab. The modern irrigation system was introduced in Rechna Doab through the construction of the Lower Chenab Canal (LCC) in 1892 (Figure 4). Presently, the Rechna irrigation network consists of five canal commands and as many inter-river link canals (Table 1 & 2). The normal flow period for the perennial canals is about 340 days per year. The outlets (moghas) from the distributaries are designed to deliver a fixed quantity of water when canal is flowing at full capacity and design flows are based on the command area. Each farmer is allotted a fixed quantity of water proportional to his land holding on a weekly or 10-days rotation period locally called "Warabandi".

Figure 5: Irrigation System of Rechna Doab

Table 1

Table 2

This system was designed to spread a limited amount of canal water over the entire area to support approximately 65 percent cropping. The major design objective of irrigation development at that time was to protect against crop failure and prevent famine. However, the cropping intensities have been drastically increased (up to 150%) after the completion of the Indus Basin Works (including three major reservoirs and some link canals) that were initiated after the signing of the Indus Basin Treaty between India and Pakistan under United Nations/World Bank auspices in 1960.

Agriculture

The Rechna Doab falls in the rice-wheat and sugarcane-wheat agro-ecological zones of the Punjab province. The soils are adaptable to a wide variety of crops and temperatures allow year-round cropping. Rice, cotton and forage dominate the summer season (Kharif: April to September), while wheat is the major winter crop (Rabi: October to March). Sugar cane is also cultivated which is an annual crop.

Threats to Sustainability of Irrigated Agriculture

Waterlogging and Salinity

The sustainability of irrigated agriculture is threatened with environmental hazards; such as waterlogging and salinization. Before the establishment of the irrigation system, the watertable in Rechna Doab was 20 to 30 meters below the ground surface. Due to conveyance losses from irrigation canals over the years, the natural hydrological balance was altered which led to the problems of waterlogging and salinity.

Figure 6 : Surface Salinity

Depleting Groundwater

Another threat to the sustainability of irrigated agriculture is the mining of groundwater resources. In fresh groundwater areas farmer are using groundwater, mostly in conjunction with canal water, for expansion of their cropped area and high cropping intensity.

Benchmark Basin Main Page

Activities and objectives

Current Benchmark Basins :

• Rechna Doab (Indus River sub-basin) - Pakistan
• Olifants - South Africa
• Ruhuna - Sri Lanaka