18. DRYLANDS

Salting and Interceptor Banks

    

9o. militate“ AREA. WA, AUSTRALIA.

Deforestation. grazing. and wheat cultivation have produced
Widespread salting, here visible as collapsed soil at seepage lines. The
bro'wnish barley greas (Hordeum maritimum) is also indicative of soil
cu apse.

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92. OUAIRADING, WA, AUSTRALIA.

A farmer develops interceptor banks to run surface water and
throughflow off fields to a natural valley. thus isolating soil blocks for
rain leaching and preventing a 'cascade' effect downhill of salty
overland flow or throughtiow,

  
   

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91. NEAR QUAIRADING, WA. AUSTRALIA.

A closer look at a once—forested marsh in wheatlands, now a saitpan.

 

93. QUAIRADING, WA, AUSTRALIA

A classic interceptor bank, ending on the streamline as marked by the
distant trees, A bulldozer has rammed subsoil on the downhill wall of
the bank. Depth = 1.5 m, width 4 m. spacing not more than 100 m
apart. or (on slopes) 1 m vertical separation. Soil pit below this bank
shows no throughtlow. no rising salted groundwater.

 

94. BEERMULLAH, WA, AUSTRALIA.

An interceptor has prevented soil collapse by flooding (note rushes on
upslope side). thus protecting crop below the bank. Spike rush
(Juncus) is another indicator of imminent soil collapse, surface
flooding, and anaerobic soils. Subsoils are dry, cemented. or subject
to groundwater rising.

95. BEERMULLAH, WA, AUSTRALIA.

A series of interceptor banks in wheatfields isolate soil blocks from
overland flow and salting effects.