AN INVESTIGATION INTO THE QUALITATIVE AND
QUANTITATIVE EFFECTS OF CLIMATE CHANGE ON RIVERS IN
IRAN
Hojat Dehghani Vahid 1, Mohammad Noori 2*, Mohammad Heydari 3, Mohammadsaeid
Sheikhi 4
1. MSc student, LameiGorgani institute of higher education, Gorgan, Iran
2 PhD of Civil engineering, Ferdowsi university of Mashhad, Mashhad, Iran
3. PhD candidate, University Malaya, Kuala Lumpur, Malaysia
4. MSc student, LameiGorgani institute of higher education, Gorgan, Iran
Abstract
The climate change phenomenon has had a negative effect on agriculture,
environment and different water resource systems, especially in rivers due its impact on
climatic factors such as rainfall, temperature and solar radiation. Ignoring climate change
studies in the hydraulic systems designs will cause severe implications. Even a minor change
in hydraulic variables will lead to tangible changes in the water resources system operation.
Therefore, the effects of climate change on rivers have been briefly studied with a conceptual
point of view.
Keywords: Climate Change, Water Resources, River Basin, Land Use, Climate Variability,
Hydrological Modeling.
1
Background
An increasing trend of the earth’s temperature and changes in the associated global
weather conditions is known as climate change [1]. Due to worldwide development, climate
studies have become even more challenging. The greenhouse gases are known as the major
driver of current climate change, and this has caused numerous problems that have affected
different parts of the world. Following the significance of the climate change issue resulted
from human activities, it has become more necessary than ever to conduct studies that
identify and reveal climate change. Currently, some studies are being conducted on climate
parameters and their enormous effects to find the causes of these changes. Some research is
also done to provide a good insight of natural- social [2, 3], economic system [4, 5] and its
sensitivity to climate change. Also, in Iran, many studies have been conducted on climate
change and its effects on various factors [6-8]. Below, the climate parameter trends such as
temperature, rainfall, wind, humidity, etc. have been evaluated in Iran from 1951 to 2005.
Recently, attention has been drawn to analyzing the time series of rainfall, temperature,
sunshine hours, etc. in order to investigate climate parameters [9].
2
2.1
The trend of changing climate parameters in Iran
Temperature
The increment of minimum temperature and maximum temperature are studied and
evaluated in a significant number of stations in Iran. The overall trend of minimum
temperature compared to the normal period of 1961-1990 has been demonstrated in the 19512005 period as shown in Figure 1. This figure proves the temperature increase in Iran.
Changes in the minimum annual
temperature ( C°)
Reducing the range of boarding changes is very prominent in most areas of Iran, for example,
in Figure 2 this range has been provided in the form of its difference of normal period from
1961- 1990. Overall, considering the process of extent profiles of temperature in Iran from
the second half of the twentieth century indicates the increasing frequency of warm events
such as warm days, and the reducing frequency of cold events such as freezing days. It
should be mentioned that most of the obtained results are consistent with the results gained
by interstate board of climate change and other collective studies.
Year
Fig1. The process of minimum temperature in Iran from 1951 to 2005 compared to the
normal period
Fig 2. Changing trend of temperature
2.2
Rainfall
The rainfall average trend in Iran has been negative from the beginning of the second
century until now. Figure 3 demonstrates the process of precipitation profiles in all static
modes in the country. As an overall conclusion, it can be asserted that a considerable part of
the research findings are mainly consistent with the interstate board of climate change.
Fig 3. Decadal trend of rainfall in period 1951- 2005
2.3
Wind
As outlined in Figure 4, the annual average of wind speed for the period of 1951 to
2005 is at a decreasing trend. This reduction is perhaps due to effective factors such as the
city’s expansion, structural changes in their surroundings, precipitation pattern changes and
other atmospheric elements. It should be noted that factors like the reduction of wind speed,
increasing population and urban development will cause a potential pollution increase in the
cities of Iran.
Fig 4. The annual average of wind speed trends from 1951 to 2005
2.4
Humidity
Through global warming, we encounter an increase in humidity in the air along with
temperature increase in many parts of the world. In order to determine the level of humidity,
the dew point temperature trend is considered a good benchmark. The linear process of dew
points at two stations is provided in Figures 5 and 6 as samples.
Fig 5. Dew point temperature trend from 1951 to 2005 compared with the normal period
from 1961 to 1990
Fig 6. Dew point temperature trend in the period 1951- 2005 compared with the normal
period of 1961-1990
3
Effects of climate change on river
Human lives have always been subjected to different natural risks all over the world.
Parts of these dangers have mainly been due to the climate change processes such as flood,
drought and severe storm events. These dangers are relatively more widespread and frequent
[10]. Nowadays the impact of climate changes on water resources is obvious, especially on
rivers. The surface water or rivers are the most crucial water resources which have a main
role in supplying water required for different activities such as agriculture, industry,
consumption and electricity production [11]. Climate changes can affect different aspects of
rivers. Among the areas that are affected by climate change are some factors like
hydrological factor, water quality, ecosystems, soil erosion and sedimentation.
3.1
The hydrological factors and floods
The effect of climate change on the hydrologic plan and management of hydro
systems could be one of the significant challenges faced by future practicing hydrologists and
water resource administrators [12]. Flooding of rivers has caused many human and financial
losses. The risks have also increased due to climate changes and human interference to the
river systems in recent times [13]. It seems that by increasing temperature and evaporation,
reducing precipitation, the flood extent has been reduced, but investigations conducted in the
past shows a different result that proved the opposite was true, because by reducing the runoff
volume, there will be a reduction in maximum flow rate of discharge, which is one of the
important reasons of climatic change. Studies have shown that the number of floods occurred
is approximately fifty times. It proves the accuracy of the contents. Moreover, the hot
weather is able to preserve more humidity, and will increase the evaporation of the wet
surfaces. Increasing the humidity in the atmosphere will lead to the aggravation of snow
precipitation and rainfall events and the increasing potential of higher river levels and the
occurrence of floods.
3.2
Discharge
The first step in water project engineering studies is the correct use of data and
information [14]. Appropriate estimation of watershed discharge has been discussed by the
specialists in a variety of construction projects and this significant issue has considerable
impact on the design of the required structures [15]. According to the obtained information,
in the spring, the reduction of snow melting and the increase in air temperature reduces the
river discharge. This means that generally, an increase in weather temperature causes
considerable changes. In mountainous and cold areas, a rise in temperature can somewhat
cause snow melting, but increasing the river flow cannot lead to considerable changes.
Table 1. The impact of climate change on river discharge
Occurrence
Impacts
Increase the air temperature and changing snow to
rain
Temperature increment along with increasing
evaporation
Activity of sunspots
Precipitation increment
Rainfall increment in warm months along with
evaporation
Changing the rain to snow in cold months
Increasing river discharge in the winter
Increasing the temperature and decreasing the winter
snow
Overall increase in the air temperature
The rapid snow melting of and air heat
Increasing the temperature and decreasing the
precipitation
Increasing the time and spatial changes
Decrement of the river flow
The change in the river course and amount of runoff
Increasing the amount of river discharge
Reducing the amount of river discharge
Reducing the amount of river discharge during the
year
Maximum flow time transfer of river from spring to
winter
Increasing the maximum moment discharge of River
Changing schedule of flow water production
Effective on the peak flow discharge
Impact on the flow discharge and flow regime
3.3
Water resources
Water is considered as one of the fundamental basis of development, economic
prosperity, and social well-being and its shortage will cause many hindrances [16].
Table 2. The impact of climate change on water resources
Occurrence
Impacts
Change of time and spatial distribution of solid and
liquid precipitation
Meteorological data series and hydrometers
heterogeneous
Precipitation pattern change
Change in hydrometeorology regime of different
regions
Error in estimating the return period discharge
Increasing the temperature along with a change in the
amount of precipitation and evaporation
Increasing the precipitation and snow melting
Increasing the temperature along with evaporation
increment and reducing the river flow
Warming up the air and reduce the snow in winter
and consequently reduction of runoff caused by the
melting of snow.
Reducing the precipitation and increasing the
temperature
3.4
Anomalies in the intensity, duration and amount of
precipitation
Reducing the duration and continuation of the
period time between drought occurrence and
outbursts
Increasing the runoff high runoff in high latitudes
*reducing the runoff and drought increment in low
latitudes
Increasing the frequency of flood occurrence
Change in the rivers regime and surface water
reservoirs
Dropping off the entrance flow to dams
Water quality and ecosystem:
Climate change is one of the key factors affecting the quality and quantity of the
water in the rivers. The water quality of the river determines the type of its consumption. The
elements and effective materials in the quality of the water are different in various discharges;
therefore, factors that change the river flow like rainfall, evaporation, temperature will also
cause changes in water quality parameters. Generally, in low in dehydration period, due to
atmospheric precipitation interruption or little rain, the amount of soluble material in the
water increases. During the full-water period the increased discharge of water is along with
more rainfall and consequently the concentration of soluble material decreases.
According to the type of region, geological studies and determining the chemical
characterization of soil, the quality parameters such as electrical conductivity, salinity, total
cations and anions and… will be affected and depending on the region will be high or low.
Many factors such as dissolved organic matters that their concentration and chemical
compound are affected by climate changes and ultra-violet rays, can also affect the
penetration depth of ultra-violet rays on natural water. The negative effect of ultra-violet rays
on the aquatic insects and water ecosystem is clear to everyone. Solar UV rays penetrate the
significant depths of ecology in water systems and affect sweet water and marine systems
from the primary producers (Phyto planktons) to consumers (Geo planktons) in the food
chain.
Table 3. The impact of climate change on water quality
Occurrences
Impacts
Temperature increment along with reducing the
precipitation
The precipitation increment along with increasing the
discharge
Reducing the water quality
The precipitation decrement
The precipitation increment along with the consistent
flood occurrence
The precipitation increment along with increasing the
discharge in the river
Increasing the temperature of the weather and the
river
The precipitation increment
Increasing the temperature along with evaporation
decrement and flow turbulence increment
Reducing the concentration of materials
dissolved in water and water quality increment
(it may change depending on the research area)
Increasing the concentration of material soluble
in water
Entering more salts into the river and reducing
its water quality
Reducing the PH of the water and increasing the
electrical conductivity
Reducing the PH of the water and oxygen
dissolved in the water
Increasing the suspended solid material in the
water
Increasing the amount of oxygen
*The river flow is the most important factor of water quality control
Table 4. The impact of climate changes on the river ecosystem
Occurrence
Impacts
Increasing the UV-B rays
Warm and drought climate
Increasing the air temperature that causes snow
melting in early spring
Weather temperature increment and subsequently
increasing the water temperature
Short term snow in winter and faster snow melting
3.5
*Negative effect on hydraulic ecosystems
*The impact of phytoplanktons to Zooplanktons and
all nutritional chain
Reducing the amount of incoming DOC to rivers
Impact on the concentrations and chemical
compound of dissolved material
Chlorophyll concentration increment
Simulating the growth of Phytoplanktons
Sedimentation:
Climate change may increase the danger of erosion, and the amount of it depends on
the environment and regional conditions. Of course, changes in wind and precipitation
patterns can affect the rate of erosion. Research has shown that rivers contain different
sediments, especially in turbulent conditions. These sediments denote the rate of erosion and
transport of materials, and are particularly important in the field studies related to dam
construction. The sedimentation level of the rivers has a rational connection with different
discharges. Therefore, in regions where the precipitation average increment is along with
increasing discharge in rivers, the amount of sediment load of these rivers will increase.
These are some of direct and indirect effects of climate change on the river system.
Therefore, assessing the impacts of climate change on the River in the coming years can
resolve problems such as sudden floods, water quality reduction, reducing the amount of
erosion and sedimentation.
Table 5. The impact of climate changes in the river sediment
Occurrences
Impacts
Increasing the average of precipitation along with
the rivers discharge increment
Decreasing the average of precipitation level along
with the discharge reduction in rivers
The weather temperature, evaporation and
transpiration
increment
and
subsequently
decreasing the runoff coefficient
3.6
Increasing the amount of sediment load of the
rivers, sedimentation and sediment transport
increment
Decreasing the level of sediment load of the rivers
Descending the amount of suspended loads
The impact of climate change on erosion:
Table 6. The impact of climate changes on the river erosion
Occurrence
Impacts
Precipitation increment along with increasing
discharge
Climate and precipitation changes resulted from the
current climate conditions
Displacement in spatial and time cores of the cold
weather waves
Change in the climate conditions and occurrence of
severe storm and precipitation
Increasing the river erosion
4
Soil erosions increment and decomposition of
organic matter and entering into the river.
Increasing the water erosion
Loss of vegetation and changing the river bed and
privacy.
Conclusion:
Climate change effects are classified into two groups; direct effects and indirect. Changing the air
temperature, precipitation increment, changing the rain to snow in cold months, decreasing the winter
snow, the rapid snow melting, increasing the time and spatial changes could be some direct impacts
of climate changes. In fact, the indirect effects are the results of direct effects. Increasing or reducing
river discharge, anomalies in the intensity, duration and amount of precipitation, changing the amount
of suspended soil material in water, changing the PH of water and negative effect on hydraulic
ecosystems are known as some samples of indirect climate change effects. In general, the effects of
climate change on the river, could be divided into quantity, quality, economical, environmental and
social impacts. Hence, in this paper, we studied the trend of changing climate parameters in Iran
especially temperature, rainfall, wind and humidity. Furthermore, the climate changes effects on
different aspects of rivers such as the hydrological factors and floods, water resources, discharge,
water quality and ecosystem and sedimentation were also studied. The findings indicate that climate
changes can affect different hydrological and meteorological parameters. Therefore, recognition of
these parameters and the amount of their influence can help decision makers to get appropriate
policies to combat the challenges of climate change.
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