Study and Design of the Givi Secondary Irrigation and Drainage Network

Narrative Description of Project

The goal of Givi Reclamation Project was to investigate potentials and constraints of water resources and land use downstream of the new Givi Dam being constructed in Ardabil Province, northwest Iran. In order to find sustainable solutions to make efficient use of resources within a gross area of  6100 hectares, the project aims at the following:

  • reclaiming land and water resources in the project area and making efficient use of them
  • Strengthening sustainable agriculture, livestock, and relevant industries
  • Employment creation and preventing mass immigration to large cities
  • Increasing residents' wages, improving life standards & eliminating deprivation

 

A number of previous national and provincial studies had shown reclamation potentials in the area. A prefeasibility study on Givi reservoir dam had been carried out by MGCE in 1996. General reclamation design along with land use studies for crop appropriateness have also been done by MGCE in 2005.

The Givi area is semi-mountainous with many steep topographical features. There are many gullies of different sizes within the region. The main stream within this area is the Sangour River with many villages laying east and west of its path.

Description of actual services provided by your staff within the assignment

Basic studies

Our irrigation engineers acquired a coherent set of basic data required for the design of the irrigation water distribution networks, including:

  • Access roads to the area
  • Climate data: including precipitation, temperature records, humidity, sunshine hours, wind records, and evaporation
  • Water resources: main source of water in the area is the Givi River which joins other streams to form the Ghezel-Ozan River south to the project area. Quality of water from this resource was investigated in the studies. A water resources management plan was devised in the final report.
  • Soil studies: extensive studies showed that there is no major issue in soils' fertility. The soil studies included (a)soil texture, (b)terrain morphology, (c)soil permeability, (d)soil eroding conditions, (e)soil cultivability classes, (f)existing land use and agriculture practice, (g)current irrigation methods, (h)current groundwater use, and (i) appropriate crop patterns for the project area.

Based on above extensive data collection and analyses, an agricultural development plan is proposed for the Givi reclamation project. Proposed crop pattern for the Givi area was set as follows:

  • Crops designated for sprinkler irrigation method: wheat, barley, corn, potato, beans, alfalfa, soy
  • Crops designated for drop irrigation method: grapes, almonds

 

The Sprinkler and Drop irrigation methods are selected by evaluating several available irrigation methods. Sprinkler method proved appropriate for more flat areas whereas the drop irrigation method showed more suitable for more steep and topographic areas. Several factors were considered for selection of irrigation method, some of them include:

Soil texture, Ground leveling required, Size of farms, Salinity, Drainage, Available water, Water quality, Crop pattern, Available energy, Sensitivity to crop change, Production quality, Meteorological factors, Cost of water, Initial investment and Operation and Maintenance costs, Social issues

Portable Sprinkler irrigation was finally devised for more flat farms and Local Irrigation by pressure regulating nozzles was considered for more steep areas.

 

Design of the secondary irrigation water distribution and drainage networks

 

General schema for the Givi reclamation project consists of four main elements:

  • Givi reservoir dam and its facilities
  • Water transmission system from the dam reservoir into downstream irrigation water distribution network
  • Primary water distribution and drainage network which itself includes pressurized transmission pipeline, integrated hydraulic structures and pumping stations
  • Secondary water distribution and drainage network which includes pressurized irrigation systems, both sprinkler and drop methods

 

A 2000 mm diameter steel pipeline transports water from the dam reservoir to the beginning of the primary irrigation distribution network. That is eight kilometers downstream of the dam. Before entering the Givi area, some of the water is diverted into the Givi Triangle area. The remainder is distributed into the Givi area. The whole Givi reclamation area is divided into a number of reclamation units. These units are designated based on property boundaries of villages, or sometimes based on topographic features. The primary distribution network initiates with an 1800 mm diameter major distributary pipe which reduces to 500 mm in diameter at the toe of the area. Some four pumping stations are designed to retain the pressure needed for water discharge through the distribution network.  Several minor pipes distribute the water towards the reclamation units.

Hydraulic design of secondary irrigation distribution network was carried out by considering applicable go