Need the best way to interconnect borewell, sump and OHT in Bangalore, Karnataka - Need advise on best pump for household use

I am looking to construct a house and intend to build a sump of 10k litres with a borewell and OHT of 5k litres sintex tank.

my contractor advised me that you can have the borewell pump water directly to the OHT and then have excess water flow down to the sump.  However, i was not sure how i would repump the sump water to OHT.  According to him direct pumping to OHT will save electricity instead of having two pumps run. 

I would like to know what is the best way to interconnect the borewell, sump and OHT.

I also would like to know the best pump for this purpose.  also, i intend to have Rain water harvesting going into the sump through the filter and excess flowing down the borewell.

Thanks

JK