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Dealing with salinity in Wheatbelt Valleys - Department of Water

Dealing with salinity in Wheatbelt Valleys - Department of Water

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Depth (m)<br />

316<br />

315<br />

314<br />

313<br />

312<br />

311<br />

Monotonically ris<strong>in</strong>g<br />

Figure 3. <strong>Water</strong> levels <strong>with</strong> accumulative annual residual ra<strong>in</strong>fall for MD03CPUMP<br />

Rate <strong>of</strong> rise = 0.04 m/yr<br />

310<br />

Mar-85 Nov-87 Aug-90 May-93 Feb-96 Nov-98 Aug-01<br />

Date<br />

Rate <strong>of</strong> fall = 0.45 m/yr<br />

Rate <strong>of</strong> fall = 0.10 m/yr<br />

Long-term trend <strong>with</strong> ARR<br />

<strong>Water</strong> level MD03CPUMP<br />

In the upper slopes (recharge areas) where the rate <strong>of</strong> groundwater recharge is high, water levels are<br />

ris<strong>in</strong>g 0.15-0.54 m/yr. For example, <strong>in</strong> cleared sandpla<strong>in</strong> areas the water levels are cont<strong>in</strong>uously ris<strong>in</strong>g.<br />

The situation may be exacerbated by local recharge from the level banks.<br />

However, piezometer MDB that is located between MDA and MDC does not exhibit a similar pattern<br />

(this is because this area is heavy-textured and does not have such a high recharge rate).<br />

Contrary to established trends, the water levels have decl<strong>in</strong>ed <strong>in</strong> MDB s<strong>in</strong>ce June 1994 and then risen<br />

<strong>in</strong> the wet year <strong>of</strong> 1999. Piezometers MD2 and MD8 located <strong>in</strong> the valley area show a steady rise <strong>with</strong><br />

m<strong>in</strong>imal seasonal response.<br />

This is probably due to the contribution from a lateral flow from the hillslopes and leakage from surface<br />

flows. MDX was ris<strong>in</strong>g at 0.30 m/yr. until mid 1994 when the rate <strong>of</strong> rise has been zero. This is<br />

possibly a delayed effect <strong>of</strong> the tree plantation.<br />

Figure 4. Shows the hydrographs for MDA, MDC and MDX. Figure 5 shows the hydrograph for Md02b<br />

and c.

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