Abstract:
lnl3anglade,h, lhe groundwater irrigation development starled in lhc 1960s and ;ince then
it has been increasing progressively especially in the Northern region. At presellt,
irrigation covers almost all the agricullural land in the region during dry period that
provide, as a source for potential evapo-transpir"tion. In this study, an auempt has been
made to analyze the impacts of progressive inigation developmenl on ellmatic parameters,
land use, cropping pattern and soil fertility. This study is mostly based on secondary data
and inrormation. Data or greater Rangpur, greater Dinajpur and Patuakhali on daily
maximum tempemlure, minimum temperature, relative humidity, evaporation and
irrigated area were used. Ranb'Pur and Dinajpllf with extensive developmenl in irrigation
were considcred as the study area and Patuakhali with very little ilTigalion was considered
as the control area. Data on soil fertility and cropping pattern were also analyzed wilh
rclation to irrigaled arca, In case of wil fertility, the analy~is was performed only within
the study area.
The results of the analy~i5 reveal that during the irrigation season (January-April), the
maximum temperature is deercasing in Rangpur and Dinajpur at a rale of 0.5°(" and
0.46"C per decade respeetivcly, ln Patuakhali, the maximum temperalure is increasing at a
rate of 0.237oC per dceadc. rhe minimum temgcrature is increasing over the years in
Rangpm and Dinajpur at a rate ofO.5GC and 0.27 C pcr decade but in case of Patuakhali, il
docs not sho\\' any definitc trend. Although, lhe evaporation is supposed to have increased
over time with Lhe increase in irrigated area but it has been observed that the rate of
evaporation i; decreasing over time at a rate of 0,038 mill and 0.507 mm per decade in
Rangpur and Dinajpur respectively. II has also beell found lhal the relative humidity is
increasing over the years at a ratc of 0.137% and 1.275% per decade in Rangpur and
Dinajpur re~pecljvely. The relative humidity of Patuakhali does not show allY definite
lrend.
Thc study has abo revealed that there ;, a positive relationship between irrigation
development and cropping pattern changes. Mostly 13oro rice is being cultivated with lhc
developmenl of irrigation. Cropping intensity in Ranb'Pur, Dinajpur and in Patuakhali in
the pre'ient dccade is 227%, 212% and 200% respectively.
The carbon contcnt in the 0-15 em soil layer mostly increa,ed in the study area. The study
arca experiences a ,harp fall in the total nilrogen content which may be due to the changes
in cmpping sy,tems. All the physiographic units showed a decline in the content of
exchange.1ble pota%ium except for greater Dinajpur. Changes in the phosphorus
availabilily in the study area are mixed.
From the FGDs, it ha~ been observed that there is .1 perception lhal the maximum
temperature is decrea,ing. The dryness of weather has also been reduced. Soil fertility ha<;
bccn ['educed as lhe land is being cultivaled continuously with the advcnt of irrigation.
The findings of the stlldy suggest that the progressive development of irrigation in the last
fort}' yeur$ has no adverse impact on the climatic parnmeters except that it ha$ reduced the
diurnal variation of temperature in the Irrigated areas, As the irrigatioll is directly related
with cropping paltern and hence with the soil fcrtility so the cropping pattern has 10 bc
chosen carefully to avoid any adverse impact on soil fertility.
