You can use the water balance equation to assess this. Try to list and quantify all the inputs into the systems. Similarly, list and quantify all outflows in the systems. This should equal to change in storage within the area. Each of the flows and stock could be assessed either through experiments or from past statistics. You need to define the time you are interested in. For annual budget, use accumulated values for the year. An example, rainfall, surface flow into the area, groundwater inflows, water added (irrigation) are some inflows. Outflows are evapotranspiration, discharge out of the area, groundwater outflow, withdrawal of water from the area. Storage could be surface storage, subsurface and groundwater storages.  

The last paper attached done within the Atlantic Coastal Plain may be helpful in using end member concentrations to separate rainfall, interflow and groundwater quantities.  I believe I have read that peat areas can have voids and underground flow networks not obvious on the surface, but do not remember the publication.  It this were true, then finding ways to separate inputs and flow networks becomes more important.   Also you might have past drainage ditches (or past peat mining efforts) that have essentially filled with peat accumulations if unmaintained for drainage that can alter drainage or storage pattern.  Topographic depressions can also be hidden by peat as these may be essentially subsurface water storage features.  If you are or have an interested groundwater hydrologist or geologist to collaborate with, those skills can be most useful in addressing your questions.  The first two papers will probably not directly apply to your question, but may give you some information or ideas.

My short term coastal work within the Okefenokee Swamp in Georgia and Florida, short term on Croatan National Forest (NF) and years on Francis Marion NF in South Carolina suggest to me that there can be some substantial variations in conditions where adequate sampling and mapping of geology and subsurface stratrigraphy are important to understanding these marine terrace systems peat accumulates locally, and if karst geology and/or faulting are involved, abnormalities are possible, for example various stream gauges on the Suwanee River actually loose flow in the downstream sections probably due to karst or faults.

If setting up research, it may be best to find locations without stratigraphy and no or limited human drainage issues that have filled in with time, but still partially functional on moving water into or out of the system as part of a hydrologic modification.  

Please make boundary condition...we collect some parameter as an input water such as rainfall, evapotranspiration, and groundwater table record. Also make drainage network like in oilpalm is about

250 hectare(as boundary condition)