Study area The study area is located in the Barind tract situated in the Northern part of Bangladesh. Tanore is a part of the greater Rajshahi district. The co-ordinates of Tanore are 24° 29′ N to 24° 43′ N in latitudes and 88° 24′ E to 88° 38′ E in longitude. The population of Tanore is about 173495. The total area of Tanore is 295.8km2 (29580ha). Total cultivable land is about 226.56km2 (22656ha). Nearly 43% of the people are involved in agricultural activities. With the expansion of irrigation in Tanore Upazila in the mid-1980s, a revolutionary change occurred in the agricultural sector of Tanore. The introduction of high-yielding varieties (HYV) paddy combined with groundwater supply for irrigation made it possible to increase the yields of rice. Single cropped agricultural lands are now producing three crops in one agricultural year after the start of groundwater extraction. The cropping intensity in Tanore is about 262% which is high compared with the national average of 180%.1 Rice in Bangladesh is grown in three distinct seasons, namely Boro (January to June), Aus (April to August), and Aman (August to December).
Estimation of consumptive use and field irrigation requirement Evaporation (ET) or consumptive use (U) is the total amount of water lost from a cropped or irrigated land due to evaporation from the soil and transpiration by the plants or used by the plants in building up of plant tissue. It is usually expressed as a depth (cm, mm) over the area.
The blaney-Criddle formula was used to determine the consumptive use requirement of rice.31,32 Considering the available data, this method was used. Other methods, eg, the Penman equation could not be used because of the lack of required data. The Blaney-Criddle formula.
RWH calculation: In estimating the volume of water from RWH from the areas where land is not cultivated, the rational formula was used as follows:
Q = CAP
where Q is the volume of water from RWH yield (m3), C is the coefficient of runoff of 0.8 for Tanore (according to BMDA), A is the land area not cultivated (m2), and P is the rainfall depth (m)
The amount of cultivated land in Tanore is 22 656×104m2 (22 656ha). The remaining land which is not cultivated is 6924×104m2 (6924ha) and hence, A= 22656×104m2.
Data collection: Rainfall data, monthly average bright sunshine hours, and temperature data of the study area were collected from the Bangladesh Meteorological Department (BMD). A number of ponds, pond dimensions, total cultivable area of the study, and consumptive use factor for rice in different months were collected from the BMDA.
The available dataset for the meteorological parameters mentioned above ranges from 2005 to 2012. The data were monitored, sorted, and bias-corrected, ie, the quality of the data was maintained by the BMD. It records three-hourly data for rainfall and hourly data for temperature. Then the data are bias-corrected and averaged for a monthly period. The monthly averaged data were provided by the BMD. There is no missing data in the above-mentioned range. The resolution of the rainfall and temperature data is 20km.