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Stratification, diel and seasonal energy transfers in M alilangwe R eservoir in the south‐eastern lowveld of Z imbabwe
Author(s) -
Dalu Tatenda,
Moyo Sydney,
Clegg Bruce W.,
Nhiwatiwa Tamuka
Publication year - 2013
Publication title -
lakes and reservoirs: research and management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.296
H-Index - 39
eISSN - 1440-1770
pISSN - 1320-5331
DOI - 10.1111/lre.12039
Subject(s) - diel vertical migration , thermocline , epilimnion , water column , morning , zoology , environmental science , stratification (seeds) , atmospheric sciences , climatology , oceanography , geology , dormancy , biology , hypolimnion , nutrient , ecology , horticulture , botany , seed dormancy , germination , eutrophication
This study provides a 9‐month record of M alilangwe R eservoir stratification and diel and seasonal energy transfers between F ebruary and O ctober 2011. The reservoir was not strongly stratified during the hot‐wet season ( F ebruary and M arch), exhibiting low dissolved oxygen concentrations of <2 mg DO L −1 in the bottom layers (<6 m depth). During the cool‐dry season, when both the air temperature and solar radiation input decreased, the water temperatures in the epilimnion and across the thermocline decreased, and the water column was very weakly stratified. In this state, the reservoir could easily be mixed, even by light winds, resulting in overturning, thereby giving the bottom water an opportunity to become aerated, as observed during the cool‐dry season. The stability was greatest when the water level was high (during midday), while it was considerably lower during the predawn hours. The calculated annual B irgean heat budget for the reservoir was 110 MJ m −2 year −1 for F ebruary to O ctober 2011. The diurnal B irgean heat budget was consistently associated with heat loss over a 24 hour period in all seasons, mostly between 0400 and 1000 h. Spearman's correlation suggests that the DO was significantly correlated with stability for the three study months (February r = 0.69, P < 0.05; June r = −0.76, P < 0.001; October r = 0.96, P < 0.001). The results of this study suggests that warming temperatures (warmer months or seasons) will result in high B irgean heat budgets, which could potentially trigger some important changes in plankton population dynamics in small reservoir, with severe water quality implications. The nutrient concentrations varied throughout the seasons.