International Journal of Geosciences, 2013, 4, 18-23 Published Online September 2013 (
Copyright © 2013 SciRes. IJG
Effects of Temperatu re upon Water Tu rnover in Fish
Ponds in Northern Thailand
Patcharawalai Sriyasak1,2, Chanagun Chitmanat1, Niwooti Whangchai1,
Jongkon Promya1, Louis Lebel2
1Faculty of Fisheries Technology and Aquatic Resources, Maejo University, Chiang Mai, Thailand
2Unit for Social and Environmental Research (USER), Faculty of Social Science, Chiang Mai University, Chiang Mai, Thailand
Email: l
Received June 2013
Fish culture in earthen ponds is an important source of income for farmers in northern Thailand. Water quality in ponds
has strong impacts on fish production farmers’ return and is sensitive to weather and climate. Low levels of dissolved
oxygen in fish ponds are major cause of mass mortality. Stratification with depth in ponds followed by rapid turnover or
exchange of surface and bottom water can expose fish to dangerously low dissolved oxygen levels. The main purpose of
this study was to observe the effects of weather on stratification and subsequent water turnover in fish ponds in northern
Thailand, especially in the winter and rainy season, when stratification was expected to be most severe. Temperature
and water quality measurements were made in fish ponds at 18 farms with depths ranged from 0.8 - 2.0 m and size of
0.16 - 0.64 ha. Measurements were made during January and May 2013. Fish farm pond sites were divided into two
groups based on elevation above sea level: low (<400 masl) and high (>400 masl) and categorized into 3 types of farm-
ing: commercial, integrated and subsistence. In lower elevation sites, water turnover occurred at night between 22.00
and 02.00 in winter and between 18.00 and 02.00 in rainy season. At higher elevation, turnover occurred in ponds be-
tween 20.00 and 22.00 in winter and between 14.00 and 18.00 in rainy season. Turnover was slower in the lower eleva-
tion than in higher elevation zones and generally occurred earlier during the rainy season than in the winter. Mean DO
in winter was significantly higher (p < 0.05) than in rainy season, whilst water temperature and amount of ammo-
nia-nitrogen during the rainy season was significantly higher (p < 0.05) than in winter. Turnover improves distribution
of dissolved oxygen through the water column and minimizes organic matter accumulation. Cloud cover during the
rainy season may have contributed to limit oxygen production and thus may have significantly affect water quality in
ponds. Fish farmers should consider more explicitly the role of temperature and cloud conditions when managing dis-
solved oxygen levels in their fish ponds. Therefore, efficient pond aeration or pond mixing strategies for reducing strati-
fication still plays an important component for providing sound pond management in tilapia production ponds.
Keywords: Climate; Temperature; Oxygen; Turnover; Fish Culture
1. Introduction
Tilapia fish culture in earthen ponds is expanding dra-
matically in Thailand [1]. Farmers, especially in the
northern area raise these popular freshwater fish under
intensive or extensive methods, in pond cages and most
commonly along with livestock under the integrated
farming scheme for local consumption and livelihood.
Currently, fish farmers face difficulties in rearing tilapia
in earthen ponds. Warmer pond temperatures due to cli-
mate change may be a contributing factor to this problem.
Temperature and dissolved oxygen (DO) have impacts
on fish production [2,3] and may be affected by weather
and climate [4,5]. Prolonged extreme hot weather fol-
lowed by a heavy rain disturbs the surface water to cool
lower temperatures where the cool heavy water layer
sink to the bottom floor due to gravity can cause turnover
of water in ponds [6,7]. Stratification with depth in ponds
followed by rapid turnover or exchange of surface and
bottom water can expose fish to dangerously low dis-
solved oxygen levels subjecting them to stress and vul-
nerability to diseases. Low levels of dissolved oxygen in
fish ponds are major cause of fish death [8]. Tilapia fish
culture in earthen ponds in northern Thailand can be di-
vided into three categories: commercial, integrated (with
pig or chicken) and subsistence. Sensitivity to lower dis-
solved oxygen in different culture systems causes differ-
ent levels of risks of mortality from changes in weather
and water turnover. The main purpose of this study was
to measure the effects of weather on stratification and
subsequent water turnover in fish ponds under different
Copyright © 2013 SciRes. IJG
culture systems and in different sites across a climate
gradient in northern Thailand so as to identify ways to
reduce risks of mass mortality under current climate as
well as adapt to a changing climate.
2. Material and Methods
2.1. Study Site
This study was carried out in 18 ponds located in 5 se-
lected provinces of Northern Thailand: Chiangrai, Chi-
angmai, Phayao, Lampang and Nakornsawan. Mean ele-
vation of these areas range from 25 to 582 meters above
sea level (masl). Pond sizes ranged from 0.16 - 0.64 ha
with depths of 0.8 - 2.0 m. Ponds were grouped accord-
ing to elevation (lower, <400 masl and higher, >400 masl)
and culture system: commercial (C), where prepared pel-
let feed was regularly provided and crops tended to be
harvested at one-time and sold; integrated (I), where fish
and livestock were being raised in the same area; and
subsistence (S), where feeding was sporadic and fish
harvested continuously for consumption and market. The
characteristics of each of culture system are further de-
scribed and summarized in Table 1.
2.2. Water Parameter
Data of water quality in ponds were collected for a typi-
cal winter and rainy months, January and May 2013.
Water temperature, dissolved oxygen (DO), pH, turbidity
and conductivity were monitored at 2-hour interval over
a 24-hour period in each season at every 20-cm depth
with a multimeter (TOA DKK WQC-22A model, Japan).
Water samples were collected 20-cm below the surface
and 20-cm just off the bottom using a modified water
sampler. Chemical analyses were carried out for Total
Ammonia-Nitrogen (TAN), Nitrite-Nitrogen (
Nitrate-Nitrogen (
-N), Orthophosphate (
Alkalinity, Total Suspended Solids (TSS) and Chloro-
phyll-a (Chl-a) according to standard methods [9].
2.3. Statistical Analysis
ANOVA was used to compare water pond parameters
across the two elevation groups and the three culture
systems. Paired sample T-test was used to compare the
differences of water quality variables between the two
seasons at p < 0.05.
3. Results and Discussion
3.1. Temperature Measurements at Sampling
Mean air and water temperatures decrease with mean
elevation across the climate gradient of sites selected for
study (Figure 1). Expectedly, observed air and water
temperatures were lower at higher elevation sites. Bi-
hourly variation of air temperature in the winter (January)
ranged between 16.5˚C and 35.83˚C (28.3 ± 4.11) and
water temperature, between 25.5˚C to 27.1˚C (26.3 ±
0.57). Monitored bi-hourly air temperature during the
rainy season (May) ranged between 22.0˚C and 37.3˚C
(28.14 ± 4.03) an d water temperature, between 29.4˚C to
31.8˚C (30.44 ± 0.80). Altitude affects the temperature of
the air because air pressure gets lower as the altitude in-
creases and so does inversely affect pond water temper a-
ture as well.
Table 1. Major properties of ponds monitored in the study.
Pond Property Culture System
Commercial (C) Integrated (I) Subsistence (S)
Pond Area (m2) 1600 - 3200 1600 - 4800 640 - 1280
Pond Depth (m) 1.20 - 1.80 1.20 - 1.50 0.80 - 1.50
Stocking Rate
(fish m2) 3 3 0.5 - 1
Culture Period (d) 30 - 90 30 - 120 120 - 240
Water Renewal 10% per day seldom No renewal
Figure 1. Air and water temperatures at different elevations above sea level.
0100 200 300 400 500 600 700
Temperature (°C)
Mean Sea Level; MSL (m)
Air Temperature
Water Temperature
Copyright © 2013 SciRes. IJG
3.2. Water Turnover in Ponds
All ponds monitored stratify diurnally. During the night
and at pre-dawn the water column is isothermal, over
mid-day it is thermally stratified but isothermal condi-
tions return with the onset of light evening winds. Max-
imum temperature was recorded at around mid-afternoon
(15:00) in all ponds irrespective of elevation and culture
system type, which is typical in a shallow aquaculture
pond system.
Integrated plots of dissolved oxygen, air and water
temperatures of ponds at lower elevation (<400 masl) for
the two seasons are shown in Figures 2(a) and 2(b).
Mean air and water temperatures in the winter ranged
from 21˚C to 35.8˚C (27.9 ± 5.2) and from 27.4˚C to
29.0˚C (28.3 ± 0.53), respectively. Mean surface DO
fluctuated between 1.05 and 11.72 mg·L1 (5.38 ± 3.84).
Maximum DO value was at 16:00 daylight hour while
the minimum values were observed at dawn (4:00 - 6:00)
which coincided with bottom DO concentration mini-
mums. Pond bottom DO fluctuated between 0.97 and
4.13 mg·L1 (2. 25 ± 1.10 ) which reaches its maximum at
20:00. Noteworthy, water turnover of ponds in the winter
occurred at 20:00 when bottom DO was at its maximu m.
Complete destratification and mixing occurred at 4:00
until 6:00 when surface and bottom DO were almost
equal and at nearly isothermal condition. On the other
hand, mean air and water temperatures recorded for the
rainy season (May) were from 27.2˚C to 37.3˚C (31.1 ±
3.5) and from 28.7˚C to 29.9˚C (30.5 ± 0.90),
respectively. Mean range of surface DO was from 0.43 to
14.69 mg·L1 (4.93 ± 4.89) whereas the mean DO range
at the bottom was from 0.30 to 2.9 mg·L1 (0.94 ± 0.78).
Water turnove r transition occurred betwe en 18:00 - 02:00.
when surface DO started to drop significantly and bottom
DO reaches its maximum and decreases thereafter. Iso-
thermal condition and complete destratification were
attained at 4:00 until 6:00 as observed in the winter.
However, water turnover occurred earlier for the rainy
season as compared during the winter. This could be due
to rain effect, cooling the surface water by a cold rain
and wind close to the temperature of deep water, allow-
ing them to mix.
In higher elevation sites (>400 masl) (Figures 2(c),
2(d)), mean air and water temperatures during the winter
was recorded to be between 16.4˚C to 29.2˚C (21.6 ±
4.78) and between 22.9˚C to 24.5˚C (23.7 ± 0.62), re-
spectively. Mean surface DO fluctuated from 3.83 to
11.44 mg·L1 (7.11 ± 2.77) while the mean bottom DO
ranged from 3.39 to 5.30 mg·L1 (4.23 ± 0.58). In rainy
season, mean air and water temperatures ranged from
23.3˚C to 29.8˚C (25.7 ± 2.7) and from 29.4˚C to 31.4˚C
(30.4 ± 0.70), respectively. Mean surface DO was 1.36 to
10.88 mg·L1 (5.32 ± 3.21) and the mean bottom DO
varied from 1.17 to 6.46 mg·L1 (3.42 ± 2.07). Th e same
pattern was observed in both higher and lower elevation
sites with respect to the relative difference in water turno-
ver occurrence between the two seasons, except only that
the difference is more pronounced in the former. Water
turnover in higher elevation sites occurred at 22:00 in the
Figure 2. Air and water temperatures, surface and bottom DO at elevations of sea level and in winter and rainy season.
6.008.0010.00 12.00 14.00 16.00 18.00 20.00 22.00 24.002.00 4.00
DO (mg/l)
Temperature (C)
Air temperature
Water temperature
DO Surface
DO Bottom
Winter < 400 m
6.008.0010.0012.0014.00 16.00 18.00 20.0022.00
DO (mg/l)
Temperature (C)
Air temperature
Water temperature
DO Surface
DO Bottom
6.008.0010.00 12.00 14.00 16.0018.00 20.00 22.00
DO (mg/l)
Temperature (C)
Air temperature
Water temperature
DO Surface
DO Bottom
Winter > 400 m
6.008.0010.00 12.00 14.00 16.00 18.00 20.00 22.00
DO (mg/l)
Temperature (C)
Air temperature
Water temperature
DO Surface
DO Bottom
Rainy > 400 m
n=9 n=7
Copyright © 2013 SciRes. IJG
winter. For the rainy season, the water turnover occurred
during daylight at 14.00 and 18.00 p.m. Due to heavy
rain during that time the water on the floor mixed with
water then sinking with lower water in the rain (Figure
2). Apparently, isothermal condition and full turnover for
both seasons at higher elevation also occurred at around
6:00 which is similar in lower elevation sites.
3.3. Water Quality in Ponds in Different Seasons
Mean values of water quality parameters for the two
seasons are presented in Table 2. Mean DO in winter
was significantly higher than in rainy season, whilst wa-
ter temperature and amount of ammonia-nitrogen during
the rainy season was significantly higher than in the
winter. It was expected though to find higher concentra-
tions of DO in ponds during cold winter months. Cold
water (lower temperature) has a higher solubility to dis-
solved gases than warm water does. A possible explana-
tion for the lower mean DO values in the rainy season
could be partly due to cloud cover limiting sunlight to
reach the water surface, thus affects photosynthesis and
oxygen production. Another is the turbidity nature of the
water at this period due to inflows from localized
run-offs and decomposition of organic matter in the wa-
ter. Moreover, ammonia and other partially degraded
decomposition products are released during the aerobic
decomposition process therefore contributed to signifi-
cantly higher ammonia-nitrogen concentration in rainy
Table 2. Physico-chemical and biological characteristics of
monitored ponds by season.
Variables Season
Winter Rainy
Temperature (˚C) 26.0 ± 2.34 a 30.4 ± 1.350 b
pH 7.25 ± 0.69 7.24 ± 3.34
DO (mg·L1) 4.81 ± 1.83a 3.39 ± 1.78b
Conductivity (mScm1) 32.30 ± 26.95 35.52 ± 28.17
Turbidity (NTU) 82.50 ± 46.97 107.32 ± 77.42
Chlorophyll-a (µg·L1) 209.61 ± 185.23 212.22 ± 226.71
NH4-N (mg· L−1) 0.188 ± 0.15a 0.415 ± 0.35b
NO2-N (mg· L 1) 0.014 ± 0.17 0.026 ± 0.04
NO3-N (mg·L1) 0.028 ± 0.03 0.090 ± 0.14
PO43-P (mg· L 1) 0.105 ± 0.21 0.058 ± 0.09
Alkalinity (mg·L1) 319.85 ± 262.77 222.94 ± 137.84
TSS (mg·L1) 55.08 ± 27.16 55.73 ± 25.68
Means followed by different letters are significantly different according to
paired t-test at p < 0.05.
No significant difference was observed for the other
water quality parameters among sampling times. Moreo-
ver, all water quality parameters analyzed were generally
within the acceptable range for fish culture.
3.4. Effects of Elevation, Culture Type and
Season on Water Quality
Multifactor-ANOVA was used to analyze the difference
of water quality in ponds at different elevation, fish cul-
ture systems and season. There were 4 main patterns ob-
served. First there was significant interaction between
elevation, culture system and season for alkalinity, con-
ductivity, turbidity and chlorophyll a (Figure 3). Com-
mercial farms have high temperature, TAN, alkalinity
and conductivity at altitudes < 400 m, but not the other
two culture systems. Second, DO was lower and TAN,
turbidity and TSS were higher in ponds in the higher
elevation group. Third, integrated culture systems had
higher turbidity, TSS and Chl-a than commercial and
subsistence culture systems; whereas commercial farms
have relatively high TAN and subsistence farms had
-N and
-N. Fourth, TAN,
-N were higher in rainy season, while pH and
conductivity were higher in winter. For all other water
parameters no significant differences were detected.
3.5. Pond Bottom Dissolved Oxygen
Measured DO concentration at the bottom of the pond
during winter was higher than the threshold value for
Nile tilapia (0.8 mg·L1 at 26˚C) (3) at all times and in all
three culture systems (Figure 4(a)). DO in commercial
ponds was consistently lower than in other culture sys-
tems, but tended to vary more in integrated than subsis-
tence ponds over the 24-hour cycle. DO at the bottom of
the pond during rainy in commercial and integrated sys-
tems were lower than the threshold of DO from midnight
to 10:00, whereas in subsistence farms it was always
above the threshold of DO (Figure 4(b)).
Commercial and integrated culture systems have high-
er risk of low oxygen concentration than subsistence
systems because both of these systems have higher fish
stocking density and feeding rate. The amount of organic
matter and waste (including excess uneaten feeds) are
expectedly high for these systems, depleting water of DO
during the decomposition of these materials at the bot-
3.6. Limitations and Future Research
This study had some important limitations that raise
questions for future research. First, the observations were
based on single dates in each season. Stronger evidence
about effects of season requires multiple observations
Copyright © 2013 SciRes. IJG
Figure 3. Water quality in ponds at different elevation and fish culture in 2 seasons.
Copyright © 2013 SciRes. IJG
Figure 4. Water quality in ponds at different elevation and fish culture in 2 seasons; (A) DO bottom in winter; (B) DO bottom
in rainy season.
within seasons, and ideally, from more than one year.
Second, the effects of rainfall, wind and other weath-
er-related phenomenon proposed as causal mechanisms
for water tur n-over patterns also require further research.
4. Conclusion
Elevation and season affect water turnover in tilapia fish
ponds. At higher elevations in the rainy season water
turnover occurs earlier probably because relatively cooler
rain lowers surface water temperature and associated
wind together increases circulation. Counter-intuitively
in the rainy season there is a greater risk of low levels of
dissolved oxygen, higher temperature and more TAN as
well as
-N and
-N in fish ponds than in win-
ter. Commercial farms appeared to be more prone to cli-
mate-related problems due to their relatively higher tem-
perature, TAN, alkalinity and conductivity at lower ele-
vation. Higher elevation ponds were likewise affected
with lower DO, TAN, turbidity and TSS. Therefore,
commercial (and integrated) farmers situated at higher
altitudes should adapt sound and effective fish culture
strategies (feed and waste reduction; use of aerators and
pond mixers) to maintain safe levels of DO in the pond
and reduce the risks of fish production losses from ex-
treme weather and to help build resilience to climate va-
riability and change
5. Acknowledgements
The work was carried out with the aid of a grant from the
International Development Research Centre, Ottawa,
Canada, as a contribution to the AQUADAPT project.
Special thanks to Redel Gutierrez of Maejo University
for editing this paper.
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Winter Rainy