Dear Ijaz, if I understand your question well, the core of the question is, if a water balance can be measured or modelled not only on the large catchment scale or in test fields like lysimeters. Usually these lysimeters are quite large (let's say 10 x 10 m) to be representative for a certain part of the catchment. My colleagues built a very small scale lab lysimeter (very small means 40 x 30 cm, but with everything: drainage layer, sampling location, soil layers, vegetation etc.), and it works. But it is clear that the edge effects have a quite significant impact on the representativeness of the results for the water balance in the lysimeter, and for that reason I use the mini lysimeter only for teaching purposes to explain to the students how to build a lysimeter, how to install the layers and how to measure the seeped water quantity. For irrigation we use a watering can with a defined amount of water. And even in this mini lysimeter we see the effects of the hydrological cycle (retention, dehydration). In any case, to obtain representative results for a catchment, I would prefer a large scale lysimeter or test field, combined with a hydrological model. Hoping, this catches the point of your question. Best regards, Petra