What Is Rain Water Harvesting?
Roof Top Harvesting : 
                                  
                                Collecting Roof Water / Water From The   Impermeable Area,  Filtering It And Storing It In The Rain Water   Harvesting Tank.  The Rain Water For The First Seven Days  Is  Not   Collected / Arrangements For  First Flush Should Be Made.  Later, The    Collected Rain Water Is Filtered Through Sand, Coal And Lime And Then   Made  Avaialble For Use. The Rain Water Harvesting Tanks Can Be Placed   Either At  Ground Lvl Or At Refuge / Service Flr Lvl In High Rise   Buildings And Then  Supplied Through Gravity . The Collected Water Can   Be Used For Primary Uses  After Purification And For Secondary Uses   After Filtration. 
Ground Water Recharge :
                                 
                                Collecting The Rain Water Falling On The Plot Of Land And  Percolating It  Into The Ground At Hydro-Geologically  Suitable Points And  Thus  Increasing The Ground Water Table and Using The Same All Throughout The Year.