WATER RESOURCES OF NIGERIA

1
WATER RESOURCES OF NIGERIA

• WMA 307
• Dr. A.O. Idowu, Dr. G.C. Ufoegbune and Dr O.Z.
  Ojekunle
• Dept of Water Res. Magt. Agromet
• UNAAB. Abeokuta. Ogun State
• Nigeria
• oojekunle_at_yahoo.com

2
Rainfall Pattern, spread and quantity. Daily,
monthly and yearly rainfall in different regions
of the country.

• Climate and Water Resources of Nigeria Factors
  affecting precipitation in Nigeria.
• Variation of Precipitation in Nigeria
• (a) Seasonal Distribution Critical months in
  terms of rainfall distribution in Nigeria.
  Infuence of the Maritime winds and Continental
  winds.
• (b) Variations in Total Annual Rainfall Regions
  of high and low rainfalls, latitudinal
  distribution, regions of anomalies and causes of
  the anomalies.
• (c) Variations in rainfall regimes What are
  rainfall regimes and causes.
• Divides of the country into different regimes,
  anomalies and causes.

3
Evapotranpiration in Nigeria

• Division of Nigeria into different
  evapotranspiration zones

4
Agencies

• Agencies Federal Ministries of Agriculture and
  Water Resources. Water Corporations, Department
  of Waterways and Navigation, River Basin
  Development Authorities, Research Institutes,
  Universities.

5
Agencies Examined

• Examination of the agencies of water development
• The Federal Government The ministry of Water
  Resources. Sectors of the Minstry- Hydrology and
  Hydrogeology Division, Dams and Reservoir
  operations and Waste water and environmental
  sanitation.
• Parastatals in form of River basin development
  authorities, functions and locations all around
  the country.
• Other agencies- PTF, DEFFRI, OMPADEC, etc.
• State gvernments as agents of water developments-
  water corporations.
• Local governments as agents of water developments
• Department of Waterways.
• Research Institutes and Universities
• Non-Governmental Agencies-
•  

6
Rivers in Nigeria

• Main rivers and their flows, average flow,
  maximum and minimum flow, annual yields. Rivers
  Niger, Benue, Ogun, Kaduna, Sokoto, Rima,
  Hadejia, Jamaire, Gurara, etc.

7
Lakes and reservoirs

• Natural and artificial lakes. Reservoirs above
  dam Kainji, Jebba, Tiga dams and reservoirs
  etc. Reservoirs behind small and medium earth
  dams in different States in Nigeria.
•  

8
Niger River

• The Niger River is the principal river of western
  Africa, extending about 4,180 km (2,600 mi). Its
  drainage basin is 2,117,700 km2 (817,600 sq mi)
  in area. Its source is in the Guinea Highlands in
  southeastern Guinea. It runs in a crescent
  through Mali, Niger, on the border with Benin and
  then through Nigeria, discharging through a
  massive delta, known as the Niger Delta of the
  Oil Rivers, into the Gulf of Guinea in the
  Atlantic Ocean. The Niger is the third-longest
  river in Africa, exceeded only by the Nile and
  the Congo River (also known as the Zaïre River).
  Its main tributary is the Benue River.

9
The Niger River basinThe Niger River basin,
located in western Africa, covers 7.5 of the
continent and spreads over ten countries (Map 1
and Table 1).
Country Total area of the country (km2) Area of the country within the basin (km2) As of total area of basin () As of total area of country () Average annual rainfall in the basin area Average annual rainfall in the basin area Average annual rainfall in the basin area
(mm)
min. max. mean
Guinea 245857 96880 4.3 39.4 1240 2180 1635
Côte d'Ivoire 322462 23770 1.0 7.4 1316 1615 1466
Mali 1240190 578850 25.5 46.7 45 1500 440
Burkina Faso 274000 76621 3.4 28.0 370 1280 655
Algeria 2381740 193449 8.5 8.1 0 140 20
Benin 112620 46384 2.0 41.2 735 1255 1055
Niger 1267000 564211 24.8 44.5 0 880 280
Chad 284000 20339 0.9 1.6 865 1195 975
Cameroon 440 89249 3.9 18.8 830 2365 1330
Nigeria 770 584193 25.7 63.2 535 2845 1185
For Niger basin 2273946 100.0 0 2845 690
10
The Quantity Entering Nigeria

• The area of the Niger River basin in Guinea is
  only 4 of the total area of the basin, but the
  sources of the Niger River are located in this
  country. The quantity of water entering Mali from
  Guinea (40 km3/yr) is greater than the quantity
  of water entering Nigeria from Niger (36 km3/yr),
  
• The most important areas of the Niger basin are
  located in Mali, Niger and Nigeria (25 in each
  of these three countries).

11
Rivers and discharges

• The Niger River, with a total length of about
  4100 km, is the third-longest river in Africa,
  after the Nile and the Congo/Zaire Rivers, and
  the longest and largest river in West Africa.
• Subdivided into Four
• The upper Niger River system
• The inner delta
• The middle Niger River system
• The lower Niger River system

12
The lower Niger River system

• Leaving the border between Niger and Benin the
  river enters Nigeria, where it is joined by
  numerous tributaries. The most important
  tributary of the Niger is the Benue which merges
  with the river at Lokoja in Nigeria. The quantity
  of water entering Nigeria was estimated at 25
  km3/year before the 1980s and at 13.5 km3/year
  during the 1980s.
• In Nigeria itself the Benue is joined by several
  tributaries, of which the ones at the left side
  originate mainly in Cameroon.
• The Benue reaches its flood level in September.
  It begins to fall in October and falls rapidly in
  November,
• Reaches its lowest level in March and April.
• From the confluence with the Benue, the Niger
  heads southwards and empties in the Gulf of
  Guinea through a network of outlets that
  constitute its maritime delta.

13
Average annual discharges of the Niger River and
its main tributaries in Nigeria over different
periods Before and After 1980
River Measuring station Average flow before 1980 (km3/year) Average flow in the 1980s (km3/year) Difference ()
Kaduna Wuya 16.5 14.8 -10
Benue Yola 25.0 13.5 -46
Benue Makurdi 94.0 74.9 -20
Benue Umaisha 108.0 76.7 -29
Niger Jebba 40.7 24.3 -40
Niger Baro 61.4 43.3 -29
Niger Lokoja 171.5 137.9 -20
Niger Shintaku 173.8 139.0 -20
Niger Idah 177.0 147.3 -17
14
The irrigation sector in Nigeria can be divided
into three categories

• public irrigation schemes, which are
  government-executed schemes farmer-owned and
  operated irrigation projects (improved
  fadamas) residual fadamas or floodplains.

15
Problems of Irrigation

• Estimating irrigation potential is rather
  difficult, despite the considerable data
  available on surface water resources, because of
  the potential of large areas to be irrigated
  either by surface water or shallow fadama
  aquifers, two sources that are hydraulically
  connected. Table 4 presents irrigation potential
  as identified in the national water resources
  master plan (NWRMP)

16
Table 4 Niger River basin irrigation potential,
water requirements, water availability and areas
under irrigation
Country with an area within the Niger basin Irrigation potential Gross irrigation water requirement Gross irrigation water requirement Actual flows Actual flows Flows after deduction for irrigation and losses Flows after deduction for irrigation and losses Area already under irrigation (ha)
per ha total inflow outflow inflow outflow
(ha) (m3/ha. year) (km3/yr) (km3/yr) (km3/yr) (km3/yr) (km3/yr)
Guinea 185000 23500 4.35 0.00 40.40 0.00 36.05 6000
Cote d'Ivoire 50000 23500 1.18 0.00 5.00 0.00 3.83 0
Mali 556000 40000 22.24 45.40 29.20 39.88 6.96 187500
Burkina Faso 5000 7000 0.04 0.00 1.40 0.00 1.37 850
Benin 100000 18500 1.85 0.00 3.10 0.00 1.25 740
Niger 222000 37000 8.21 33.70 36.30 9.58 3.96 67520
Cameroon 20000 18500 0.37 0.00 13.50 0.00 13.13 2000
Nigeria 1678510 10000 16.79 49.80 177.00 17.09 rest to sea 670000
Sum of countries 2816510 55.02 924610
Total for Niger basin lt 2816510
17
Rivers to the Countrys Coast

• The river catchment basins in the coastal zone
  consist of
• the western Nigeria catchment basin,
• the Niger Benue catchment basin,
• and the south-eastern catchment basin.
• The major rivers in the western Nigerian
  catchment basin consist of Ogun,
• Owena,
• Osun
• and Shasha which are sourced from the Yoruba
  highlands and drain the landmass in the south
  western part of Nigeria.
• These rivers empty into the Lagos lagoon.

18
Niger Benue catchment

• The Niger Benue catchment basin is dominated by
• the Niger and Benue rivers.
• The Niger River flowing over coarse, crystalline,
  Cretaceous and Cenozoic base complex enter the
  country in the west,
• and has a total length of 4 123 km - making it
  the eleventh longest river in the world.

19
Other Tributaries

• At Lokoja, the Niger River is joined by the River
  Benue before continuing its course due south into
  the Gulf of Guinea. Other important tributaries
  of the Niger include
• Rivers Sokoto,
• Zanfara
• and Kaduna.
• Some 233 km below the Lokoja at Aboh, the Niger
  River starts to break up into tributaries to form
  a delta. The Niger River drains a total area of
  621,351 km2. NEDECO, (1961) estimated the annual
  discharge of freshwater to the delta to be 200 x
  109 cubic metres, while total annual discharge
  has also been estimated to be about 300 x 109
  cubic metres.

20
The South Eastern Catchment

• The south eastern river catchment basin is
  drained by
• Imo River,
• Calabar and
• several other smaller rivers which take their
  sources from the eastern highland south of the
  Benue River. These rivers empty into the ocean
  through estuaries.

21
Lake and Dams in Nigeria

• The Challawa Gorge Dam is in Kano State in the
  Northeast of Nigeria, about 90 km southwest of
  Kano city. It is a major reservoir on the
  Challawa River, a tributary of the Kano River,
  which is the main tributary of the Hadejia River.
• The dam is owned and operated by the
  Hadejia-Jamaare River Basin Development
  Authority, a Federal agency.
• It is 42 m high and 7.8 km in length. The dam has
  a full storage capacity of 904,000,000 m3. The
  direct catchment area is 3857 km2.

22
Usefulness and Issues (Challawa Gorge Dam) Cont

• Hydro power potential
• 3. Issues
• Not stabilized
• Siltation.
• Disruption of the natural balance along the
  river.

23
Kafin Zaki Dam

• The Kafin Zaki Dam is a controversial project to
  build a reservoir on the Jama'are River (also
  called the Bunga River in its upper reaches) in
  Bauchi State in the Northeast of Nigeria.
• Proposed dam and reservoir The proposed dam
  would be of zoned earthfill construction and
  would be 11 kilometres-long. It would be designed
  with the
• potential to install a hydroelectric plant.
• As reservoir
• Second largest in Nigeria after the Kainji Dam.
• For irrigation
• Potential for sugarcane production
• Provide over one million jobs in industries
  related to agriculture.

24
Kafin Zaki Dam (Cont)

• Controversy Impact downstream flow.
• prevent the seasonal floods that their farmers
  depend upon for farming,
• Cause drop in water
• Environmentalists are also concerned about the
  impact on downstream wetlands.

25
Kainji Dam

• Kainji Dam Reservoir on the Niger River, on the
  border between Niger and Kebbi states, in western
  Nigeria Kainji Dam is a dam across the Niger
  River in western Nigeria
• and covers an area of 1,300 square km
• it is used extensively for fishing and
  irrigation.
• The lake completely submerged Foge Island in the
  Niger River, the town of Bussa, and other
  riverine settlements part of the old town of
  Yelwa (the seat of Yauri emirate) was also
  permanently flooded. About 50,000 peoplemostly
  Reshe (Gungunci, Gungawa), Busa (Busawa,
  Bussangi), Kamberi, Nupe, Lopawa, and Larowere
  displaced.
• Construction of the dam began in 1964 and was
  completed in 1968.
• The total cost was estimated at 209 million,
• with one-quarter of this amount used to resettle
  people displaced by the construction of the dam
  and its reservoir, Kainji Lake.
• The dam is one of the longest dams in the world

26
Kainji Dam (Cont)

• Dimensions Kainji Dam extends for about 10 km,
  including its saddle dam, which closes off a
  tributary valley.
• Most of the structure is made from earth, but the
  center section,
• housing the hydroelectric turbines, was built
  from concrete. This section is 65 m (215 ft)
  high.
• Capacity The dam was designed to have a
  generating capacity of 960 Megawatts
• however, only 8 of its 12 turbines have been
  installed, reducing the capacity to 760
  Megawatts. The dam generates electricity for all
  the large cities in Nigeria. Some of the
  electricity is sold to the neighboring country of
  Niger.
• In addition, occasional droughts have made the
  Niger's water flow unpredictable, diminishing the
  dam's electrical output.
• The dam has a single-lock chamber capable of
  lifting barges 49 m (160 ft).
• Lake Kainji Kainji Lake measures about 135 km
  (about 84 mi) long and about 30 km (about 19 mi)
  at its widest point,

27
Tiga Dam

• Tiga Dam Catchment area of the Yobe River, The
  Tiga Dam is in Kano State in the Northeast of
  Nigeria, constructed in 1971-1974. It is a major
  reservoir on the Kano River, the main tributary
  of the Hadejia River. Water from the dam supplies
  the Kano River Irrigation Project as well as Kano
  City. Several studies have shown that the dam has
  delivered negative economic value when its effect
  on downstream communities was taken into account.
• The Hadejia-Nguru wetlands further downstream
  have considerable economic and ecological
  importance. They are home to about one million
  people living by wet-season rice farming,
  agriculture at other seasons, fishing and cattle
  grazing by Fulani people. The dam has damaged the
  cycle, reducing fish catches and harvests of
  other wetland products.

28
IMPACTS OF DAMS

• Ecological impact of dams
• Emission of Greenhouse Gases (GHG)
• Alteration of Flow Regime
• Biodiversity Loss
• Social Impact
• Gender-Related Impacts
• Impact of Cultural Heritage
• Health Related Impacts

29
DAM DISASTERS IN NIGERIA

• Shiroro Dam Over 26 villages in Kede, Lakpma and
  Shiroro Local Government in Niger State were
  flooded by the waters from Rivers Niger and
  Kaduna in 2003. The flood displaced about 10,000
  persons in Ketsho in Kede Local Government who
  were said to have moved to Kwara State, while
  other 13,500 person in Lakpam and Shiroro were
  rendered homeless.
• Obudu Dam The Obudu Dam spillway was damaged by
  storm in July 2003 which resulted in fatal
  disaster that claimed over 200 houses, several
  farmlands, settlements and business concerns.
• Igabi Dam Property worth about N500 million
  (3.9m) were destroyed while thousands of people
  were rendered homeless in Kaduna State when River
  Kaduna overflowed its banks and submerged several
  streets and housing estates. The flood was caused
  by the collapse of Igabi Dam.

30
DAM USES IN NIGERIA (Cont)

• Dam Uses
• MP Multipurpose use
• WS Water supply
• RC Recreation
• IR Irrigation
• NA Not available

31
Groundwater Exploitation Through Tube wells and
Boreholes

• The availability of ground water for the
  development of any State or Community in the
  country depends on the hydrogeological
  characteristics of the underlying ground water
  province in the area. It is therefore necessary
  to study, identify and evaluate the water
  resources of the hydrogeological province in any
  area and develop an exploitation strategy that
  best suites the province.

32
Examples of hydrogeological characteristics

• Coastal Alluvium is restricted to the Coastal
  States like,
• Cross River, Akwa-Ibom Rivers, Bayelsa, Delta,
  Edo, Ondo, Ogun and Lagos States.
• The River Course Alluvium traverses the whole
  country following the various rivers systems
  draining the country.
• While the Coastal Sedimentary areas underlie the
  southeast States of Imo, Anambra Abia, Enugu,
  parts of Delta,
• While the Crystalline Area or Basement, occupies
  most of the Sahelian northern States Like, Kano,
  Bauchi, Kwara, Oyo, Niger, Kaduna Plateau,
  Adamawa, Taraba etc.,
• the Basement Complex hydrogeological Province,
  occupies nearly half and most of the Central area
  of the Country..

33
Notes

• It is therefore apparent that despite the obvious
  poor hydrogeological properties of the
  Crystalline or Basement Complex province, the
  area cannot be ignored in the Water Resources
  Development of the Country.
• Similarly, despite, the apparent good ground
  water prospects of the Sedimentary regions,
  problems like, Saline intrusion in the Coastal
  areas, depth of occurrence and the predominance
  of impermeable shales and clays in the
  sedimentary sequence present obstacles in the
  ground water development of those areas of the
  country

34
Tube wells and Boreholes

• Depth for depth on any given site, hand-dug wells
  may yield more water than tubewells,
• Xteristies of Tubewell
• 100 or 150 mm diameter
• are usually quicker and cheaper to sink,
• need no dewatering during sinking,
• require less lining material,
• are safer in construction and use,
• and involve less maintenance.
• From a hygienic point of view, the fact that a
  pump is needed to lift water from a tubewell is
  an asset, not a liability.

35
Features of Tubewell and Technological Equipment

• This section describes some features of tubewells
  which have handpumps, and two methods of sinking
  them in generally soft ground
• Equipment
• using only man-powered low-technology equipment,
  namely, hand auguring using a Vonder rig, and
  sludging.

36
The casing

• Use PVC, "down-the-hole", which can be lifted out
  for maintenance or repair.
• Seepage down the tubewell bore is prevented by
  the sanitary seal. Seepage from the ground above
  the aquifer is excluded by the lengths of plain
  casing. Water to be pumped is admitted through
  slots in the lower lengths of casing.
• Casing to support the external surfaces of the
  borehole against collapse may be needed, either
  temporarily or permanently, but is not shown.
• Water abstracted from aquifers in relatively soft
  ground usually contains sand or silt particles,
  which are liable to cause rapid wear to pump
  valves and cylinders (and dissatisfaction among
  consumers).

37
Methods of preventing these particles from
reaching the pump

• Screening
• Sand/gravel packing.

38
Developing the well

• Over-pumping (that is, pumping at above the
  design-rate) before the well enters service can
  improve the efficiency of the packing by drawing
  further fine particles into it. Where the
  surrounding ground has many fine particles, the
  flow of water can be accelerated by back-flushing
  at a higher rate. 
• This over-pumping and back-flushing is known as
  developing the tubewell.

39
Sinking tubewells

• At least two experienced operators are required
  communities will usually supply unskilled labour.
  Samples of the excavated material should be taken
  at regular intervals of depth (and also if the
  strata changes) and a borehole record should be
  kept.
• Particular attention is needed to maintain
  verticality. A "down-the-hole" pump which has
  been installed out of the vertical may be hard to
  operate and subject to excessive wear.

40
Auguring

• Auguring cuts earth away by the rotation of a
  cylindrical tool with one or more cutting edges.
  The excavated earth feeds upwards inside the tool
  body, which needs lifting to the surface for
  emptying at intervals.
• This requires the whole auguring (drilling) train
  to be uncoupled and lifted the weight involved
  can be considerable, and puts a limit to the
  depth of hand-operated auguring.

41
Auguring using the Vonder Rig

• The Vonder Rig, can sink a tubewell hole up to
  170mm in diameter and about 115m deep in about
  two days in ground which is predominantly soft.
  The next drawing shows its salient parts, all of
  which are made of mild steel and can be carried
  by hand between sites.
• The crossbar is friction-bolted to a stem, at a
  height suitable for pushing round by hand.
  Helpers can sit on it if auguring needs extra
  weight (or even if it doesn't). Additional stem
  sections are added as auguring proceeds.
• Several shapes and sizes of auger-bit are
  provided, including a "hole-saw" this is
  intended to tackle soft rock, but has rarely been
  successful. Thin layers of rock have been
  penetrated, however, by an improvised arrangement
  including a slow-speed diesel drive to the
  drilling train.

42
Sludging

• Sludging is an effective method of sinking
  tubewells.
• Sludging is a cheap but effective method of
  sinking small-diameter tubewells to a great depth
  in the water-logged silts and fine sands which
  underlie some flat river plains and deltas,
  notably those in the Indian subcontinent
• Tubewells 25mm and upwards in diameter (the
  larger ones are able to accommodate a
  "down-the-hole" pump) are sunk to depths of 60m
  or more. A boring pipe, usually a galvanised mild
  steel tube fitted with a case-hardened open
  socket at its base, moves vertically under the
  action of a bamboo lever pivoted on an H-frame.
• For the duration of each upstroke, another man
  seals the open top of the pipe with his hand,
  creating a partial vacuum inside it, so that the
  water within the pipe rises with it. He removes
  his hand for the downstroke, during which the
  pipe drops faster than the water inside it. As
  this hand-on / hand-off cycle repeats, water
  starts to gush from the top of the pipe and the
  whole assembly begins to work as an elementary
  force pump.
• Additional lengths of boring pipe are attached
  successively until the required depth is reached.
  The whole pipe is then withdrawn and replaced by
  PVC rising main (for a suction pump) or PVC
  casing (for "down-the-hole" pumps).

43
Other methods of drilling

• WaterAid prefers the simplest methods of
  drilling, particularly those which can be
  operated by villagers themselves. However, there
  are several other, more complicated, techniques
  which can be used and the next few diagrams
  illustrate the following methods
• Percussion drilling
• Rotary percussion drilling
• Rotary drilling with flush
• Jetting

44
Tidal and Saline water in Coastal areas

• Coastal Geomorphology and Habitat The Nigerian
  coastal and marine area consists of a narrow
  coastal strip of land bordered by the Gulf of
  Guinea of the Central Eastern Atlantic. The
  coastal areas stretch inland for a distance of
  about 15 km in Lagos to about 150 km in the Niger
  Delta and about 25 km east of the Niger Delta.
• The Nigerian coastal area is divided into four
  main geomorphic zones (figure 1) namely
• Barrier Lagoon Coast
• Mahin Mud Coast
• Niger Delta
• Strand Coastline

45
Xteristics of Niger Delta

• The Niger delta spreads over a number of
  ecological zones sandy coastal ridge barriers,
  brackish or saline mangroves, freshwater
  permanent and seasonal swamp and lowland forests.
• The mangroves and wetlands along the major
  estuaries between Benin river in the west and
  Cross River in the east have a total brackish
  area of 2 520.79 km2

46
Coastal Currents and Tides

• The Nigerian coast and marine areas are
  influenced by tides, waves, long shore currents,
  and ocean currents.
• Tides along the entire Nigerian coast are semi
  diurnal with two tides arrive in a south westerly
  direction. Tidal range varies from 1m at Lagos
  and increases progressively eastwards to about 3
  m at Calabar. Intense tidal activities are more
  destructive along the Mahin coast during spring
  tides, during which tidal range reaches 1.5m.

47
Saline

• Water is classified as "saline" when it becomes a
  risk for growth and yield of crops. Saline water
  has a relatively high concentration of dissolved
  salts (cations and anions). Salt is not just
  "salt" as we know it - sodium chloride (NaCl) -
  but can be dissolved calcium (Ca2), magnesium
  (Mg2), sulfate (SO42-), bicarbonate (HCO3-),
  Boron (B), and other compounds.
• Water can be both saline and sodic, or
  saline-sodic. If water has an EC greater than 4
  (2 for horticulture) and a Sodium Adsorption
  Ration (SAR) greater than 12, it is considered
  saline-sodic
• The concentration is usually expressed in parts
  per million (ppm) of salt.
• If water has a concentration of 10,000 ppm of
  dissolved salts, then one percent (10,000 divided
  by 1,000,000) of the weight of the water comes
  from dissolved salts.

48
Classification of Salinity

• Slightly saline water contains around 1,000 to
  3,000 ppm.
• Moderately saline water contains roughly 3,000 to
  10,000 ppm.
• Highly saline water has around 10,000 to 35,000
  ppm of salt.
• Seawater has a salinity of roughly 35,000 ppm,
  equivalent to 35 g/L.

49
Salinity in Different Water Bodies
Water salinity based on dissolved salts in parts per thousand (ppt) Water salinity based on dissolved salts in parts per thousand (ppt) Water salinity based on dissolved salts in parts per thousand (ppt) Water salinity based on dissolved salts in parts per thousand (ppt)
Fresh water Brackish water Saline water Brine
lt 0.5 0.5 30 30 50 gt 50
50
Effects of Salinity

• Saline water reduces plant growth to varying
  degrees, with grass and grain crops generally
  showing less sensitivity and field crops being
  most sensitive. Aside from biomass reduction,
  salinity can have additional effects on plants.
  For example, in a study by Bauder et al., both
  inoculated and non-inoculated alfalfa were grown
  with irrigation waters of progressively higher
  salinity levels
• Correction of Salinity
• There are no amendments, chemicals, or additives
  available commercially that can be added to
  saline water to make the salt go away. Dilution
  with a non-saline water or salt precipitation
  with an evaporation process which leaves the salt
  behind and traps the evaporated water can be
  used. Dilution of saline irrigation water is only
  possible if there is a source of non-saline water
  with which to dilute the saline water