$6.$ To remove the excess water from a locality, tile drainage system is proposed. The hard stratum is $8$ m below the ground surface and there are two layers of soil below the ground surface. The average coefficient of permeability is $\backslash (0\mathrm{.}0025\backslash$mathrm$\{$~cm$\}/\backslash$mathrm$\{$sec$\}\backslash ).$ The tile drains will be installed such that the centreline of tile drains will coincide with the interface of two layers of soil. $($a$)$ Determine the spacing between the tile drains; $($b$)$ Find the total discharge per unit length carried by the drain. $(4+2$ marks$)$

$\backslash$begin$\{$tabular$\}\{|$c$|$c$|$c$|$c$|$c$|$c$|\}$

$\backslash$hline Year & $\backslash$begin$\{$tabular$\}\{$c$\}$

Annual $\backslash \backslash$

Rainfall $\backslash \backslash$

$($mm$)$

$\backslash$end$\{$tabular$\}$ & $\backslash$begin$\{$tabular$\}\{$c$\}$

After drainage $\backslash \backslash$

the maximum $\backslash \backslash$

water table $\backslash \backslash$

level below $\backslash \backslash$

GL $($m$)$

$\backslash$end$\{$tabular$\}$ & Year & $\backslash$begin$\{$tabular$\}\{$c$\}$

Annual $\backslash \backslash$

Rainfall $\backslash \backslash$

$($mm$)$

$\backslash$end$\{$tabular$\}$ & $\backslash$begin$\{$tabular$\}\{$c$\}$

After drainage $\backslash \backslash$

the maximum $\backslash \backslash$

water table $\backslash \backslash$

level below $\backslash \backslash$

GL $($m$)$

$\backslash$end$\{$tabular$\}\backslash \backslash$

$\backslash$hline $2022$ & $1847$ & $1\mathrm{.}6$ & $2015$ & $2033$ & $1\mathrm{.}55\backslash \backslash$

$\backslash$hline $2021$ & $1948$ & $1\mathrm{.}65$ & $2014$ & $1556$ & $1\mathrm{.}85\backslash \backslash$

$\backslash$hline $2020$ & $2074$ & $1\mathrm{.}5$ & $2013$ & $1103$ & $2\mathrm{.}15\backslash \backslash$

$\backslash$hline $2019$ & $1382$ & $1\mathrm{.}9$ & $2012$ & $1002$ & $2\mathrm{.}2\backslash \backslash$

$\backslash$hline $2018$ & $1668$ & $1\mathrm{.}8$ & $2011$ & $1237$ & $1\mathrm{.}95\backslash \backslash$

$\backslash$hline

$\backslash$end$\{$tabular$\}$