RiverSalt A spreadsheet program

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RiverSaltA spreadsheet program

• Water and salt balances along rivers in
  (semi)arid zones that provide water for
  irrigation and receive drainage return flow

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River salinity increases to harmful levels
downstream

• In irrigation projects along the river the salt
  concentration of the water increases due to
  evaporation
• The flow of drainage water returned to the river
  is also more saline and spoils the quality of the
  river water
• Further downstream the soils may become too
  saline and agriculture suffers.

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Downstream river salinity in Egypt and Pakistan

• Egypt has a long and big river the Nile. Its
  waters are used for extensive irrigation.
  Downstream, in the North of the Nile Delta, the
  irrigation water is salty and agricultural lands
  are barren due to soil salinity.
• Pakistan also has a long and big river the
  Indus. Downstream, in Sindh province, the
  irrigation water is salty and many lands are
  barren due to soil salinity
• In Egypt the available amount of irrigation water
  per ha is more than in Pakistan.
• Therefore in Pakistan the problem is more serious
  than in Egypt

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Example of salt import in irrigation project

• Good quality water 0.5 g salt / l water
• EC 0.75 dS/m
• Irrigation 10 000 m3 per ha per year
• Salt import is 5000 kg per ha per year
• When salinity is 1 g/l and irrigation is 20000 m3
  (sugar cane) then import is 20 T

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Example of soil and return flow salinity

• If irrigation efficiency is 90 (very high), then
  10 of the irrigation water is drained an
  returned to the river.
• If salinity irrigation water is 1 dS/m
  (reasonable quality) and leaching efficiency is
  100, then soil salinity is 10 dS/m (saline soil)
  and salinity of return flow is also 10 dS/m
• If leaching efficiency is 50, then soil salinity
  is 20 dS/m (very saline).

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Schematic diagram of river with irrigation
projects, return flow, and salinity
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Application to reality

• The previous diagram has been used in the
  spreadsheet program SaltyRiver. This will be
  shown later.
• Adaptations of the spreadsheet to local
  situations can be made without much difficulty
• This gives a tool for
• monitoring river and soil salinity
• simulate the effects of different measures for
  salinity control
• predict the effects of new developments
• For more accuracy one can use the
  agro-hydro-salinity model SaltMod in each
  irrigation project separately to determine soil
  and drainage salinity more precisely

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Soil salinity control

• In Egypt and Pakistan outfall drains are used to
  take the salty river water to the sea instead of
  returning it to the river
• In Australia and USA evaporation ponds
  (artificial lakes) are used so that drainage
  water is evaporated instead of returning it to
  the sea
• In India land is sacrificed (also called
  retired) part of the agricultural land is
  taken out of use or put under salt tolerant
  trees and allowed to become saline. Evaporation
  occurs by capillary rise.
• For Garmsar I proposed a combined system of
  drainage and strip cropping

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Conclusions

• The optimal management of river water,
  irrigation, drainage for salinity control
  consists of a combination of measures adjusted to
  local conditions
• The interactions are complex
• It is useful to apply simulation models as a tool
  to assist the managers to reach the optimal
  decisions.
• Now we will demonstrate the SaltyRiver program