CHAPTER 3

SYSTEM DESCRIPTION

3.1 Introduction

The reservoirs play a very important role in meeting the water demands

for power, irrigation, domestic and industrial water supply, inland navigation and

tourism sectors in Kerala State, south - west India. Highly varying temporal distri-

bution of rainfall in the region makes the role of reservoirs all the more important.

Twelve reservoirs forming part of seven HEPs exist in the Periyar river basin situ-

ated in the central part of Kerala (Table 3.1). Since the water from the Idukki HEP

in the Periyar basin - the largest such project in the State - is transferred to the

adjacent Muvattupuzha river basin, both these basins are considered as one system

for the present study (Figure 3.1).

24

Chapter 3. SYSTEM DESCRIPTION

3.2 Characteristics of the Periyar - Muvattupuzha river

system

The Periyar-Muvattupuzha system falls between 090 15′ and 100 30′ N

latitude and 760 00′ and 770 30′ E longitude. The Periyar river basin with a catch-

ment area of 5398 km2 is flanked by the Chalakudy river basin on the north and

the Muvattupuzha and Pamba river basins on the south (Figure 3.1). The Periyar

river is the longest river in Kerala with a length of 244 km. From its source at

1850 m above the mean sea level (amsl), the Mullayar flows down traversing 48 km,

and joins the Periyar from its right at an elevation of 850 m amsl. The Periyar river

continues to flow towards the west for another 16 km and joins the Mullaperiyar

reservoir. The Mullaperiyar dam was constructed in 1896, which gave birth to the

Periyar lake, famous for its wildlife and tourism. The water from this reservoir

is diverted to the adjoining Tamil Nadu State mainly for irrigation and partly for

power generation. The spillover from this reservoir reaches the Idukki reservoir of

the Idukki HEP which has an effective storage of 1459.4 MCM. It is located at an

elevation of 540 m amsl. The Periyar then flows through the midland and lowland

and finally joins the Vembanad - Kol wetland system.

The tailrace from the Idukki project, after harnessing power, is diverted

to the Muvattupuzha river basin located on the southern side of the Periyar river

basin. Because of the above mentioned two interbasin transfers, the catchment of

the Periyar river basin contributing to the water downstream is virtually brought

down to 3665 km2, where as the effective catchment of the unaltered Periyar river

basin is 5398 km2 (Water Resources of Kerala, 1974). Several small HEPs were

developed in the Periyar river basin before the commissioning of Idukki HEP. The

Idamalayar HEP with an effective storage capacity of 1017.8 MCM and the Lower

Periyar HEP in the Periyar mainstream with an effective storage capacity of 4.55

MCM were commissioned after the Idukki HEP in the Periyar river basin, which

are regulations within the basin.

25

Chapter 3. SYSTEM DESCRIPTION

The Vembanad wetlands - a Ramsar site with rich biodiversity, the Cor-

poration of Cochin, and the fast growing industrial belt of Kerala in and around

Alwaye are located in the lower reaches of the Periyar basin. Two major irrigation

projects, namely the Periyar Valley Irrigation Project (PVIP) and the Idamalayar

Irrigation Project (IIP) are located in this river basin. Several rural and urban wa-

ter supply schemes under Kerala Water Authority (KWA) depend on this river for

freshwater needs. Tourism and inland water transport are other two sectors which

depend on the Periyar river (James et al. 1999, Irrigation Division, 2003).

Figure 3.1: The Periyar-Muvattupuzha river system

The Muvattupuzha river is also a perennial river. It originates from the

26

Chapter 3. SYSTEM DESCRIPTION

Western Ghats and flows through the highland and the lateritic midland and fi-

nally joins the Vembanad estuary. The length of the river is 121 km and it has a

catchment area of 1,554 km2. The Muvattupuzha river basin is bounded by the

Periyar river basin on the north and the Meenachil river basin on the south. Con-

siderable changes have taken place to the flow characteristics of the Muvattupuzha

river after the commissioning of the Idukki HEP in 1976. The Thodupuzha tribu-

tary of Muvattupuzha river receives the tailrace from the Idukki HEP. The tailrace

discharge from the Moolamattom powerhouse of the Idukki HEP ranges between

19.83− 78.5 m3/sec. (Gopinath 2003).

The Kothamangalam, Kalyar and Thodupuzha tributaries join together

to form the Muvattupuzha river. The Thodupuzha tributary is the receptor of

the tailwater from the Moolamattom powerhouse of the Idukki HEP. The power

production at the Moolamattom powerhouse is continuous throughout the year.

Because of this, flow of good quality water is always available in the river even in

summer. The water from the Periyar is diverted to the underground power house of

the Muvattupuzha river basin mainly to gain more head for power generation. Both

the Kothamangalam and Kaliyar rivers join near Muvattupuzha town and forms

the Muvattupuzha river. The Muvattupuzha river bifurcates into Ittupuzha and

Murinjapuzha branches in the downstream and finally joins the Vembanad wetlands

(Gopinath 2003).

The major area of the Periyar-Muvattupuzha river system falls under the

highland and midlands (between 7.6 and 76 m amsl) of Kerala State(Balakrishnan

2009, Gopinath 2003). The lowland (< 7.6 m amsl) in the downstream is a narrow

belt almost parallel to the shoreline. The width of the lowland ranges from 8 to

15km. Broad valleys, flood plains with swamps/ marshes and subdued sand dunes

are the major landforms of this narrow coastal region. A network of canals connect

different parts of the lowland to the Vembanad wetland system (Balakrishnan 2009).

27

Chapter 3. SYSTEM DESCRIPTION

3.3 Hydroelectric Projects (HEPs) in the Periyar-Muvattupuzha

river system

Figure 3.2 furnishes a the schematic diagram of the hydroelectric projects

in the Periyar-Muvattupuzha system. Salient features of HEPs in the study area

are given in Table 3.1(KSEB 1996).

Figure 3.2: System of reservoirs in central Kerala

28

Chapter 3. SYSTEM DESCRIPTION

Table 3.1: Salient features of HEPs in the Periyar-Muvattupuzha river system

Name of Name of Free Effective Power

HEP dam catchment storage generation

(year) (km2) (MCM) capacity

(MW)

Mullaperiyar 624 443.23 140

(1896)

Pallivasal Kundala 36.26 7.78 15

(1947)

Mattupatty 67.34 55.21 22.5

(1957)

C.P.R 129.75

Head Works

Sengulam Sengulam 5.18 0.70 48

(1954)

Neriyamangalam Kallarkutty 81.6 5.49 45

(1961)

Panniyar Ponmudi 221.445 47.4 30

(1963)

Anayirankal 64.75 48.98 -

(1965)

Idukki Idukki 649.31 1459.43 780

Cheruthoni

Kulamavu

(1976)

Idamalayar Idamalayar 380.73 1017.80 75

(1987)

Lower Periyar Lower Periyar 181.3 4.55 180

(1997)

29

Chapter 3. SYSTEM DESCRIPTION

3.3.1 Interbasin and intrabasin water transfers

The interlinking of rivers is aimed at linking surplus rivers with the defi-

cient rivers so that the excess water from surplus region could be diverted to deficient

region. This would improve water availability for drinking, irrigation and industrial

purposes in the receiving basin. Floods are moderated in the diverted basin to a

certain extent. Other than the two major interbasin transfers under the Idukki HEP

and the Mullaperiyar project, small transfers also exist in the basin. The details

of present and proposed interbasin water transfers from the Periyar river basin are

given in Table 3.2

Table 3.2: Existing and proposed interbasin water transfers from the Periyarriver basin*

Name of project Water export to Annual utilization (MCM)

Existing projects

Periyar Dam Vaigai 623 (Irrigation,63850 ha)

Idukki HEP Muvattupuzha 1271

Lower Nirar Bharathapuzha 71

Upper Nirar Bharathapuzha 255

Ongoing projects

Idamalayar Chalakudy 201

Irrigation Project (Irrigation,14394 ha)

Idukki stage III Muvattupuzha 310

Narakakkanam Muvattupuzha 6

diversion

*Source: Irrigation Division,Ernakulam,Water Resources Department 2003

30

Chapter 3. SYSTEM DESCRIPTION

3.4 Surfacewater utilization in the Periyar-Muvattupuzha

system

In the Periyar-Muvattupuzha system, summer flow augmentation by

HEPs resulted in several sectors depending more on the rivers for fresh water needs.

Data collected from different departments/agencies were integrated with the primary

data collected from the field and a schematic line sketch detailing water utilization

pattern in the system by various sectors was prepared (Appendix 3).

The schematic line diagram (Appendix 3) shows the interbasin and in-

trabasin regulations in the system, stream gauging sites, location of intakes for

domestic and industrial water supply, lift irrigation schemes and diversion structure

of major irrigation projects. Canal networks, location of major urban centres and

water quality monitoring sites are also shown. The present water withdrawal is

given sectorwise in tables. This diagram highlights the positive side of streamflow

regulation by HEPs. Dependable streamflow in the adjoining Muvattupuzha basin

multiplied several times because of interbasin water transfer. The interbasin trans-

fer reduced the salinity intrusion during the summer and supported development

of several domestic water supply schemes downstream of the Muvattupuzha river.

This river also meets the freshwater needs of a major paper industry, the Hindustan

Newsprint Limited, located in the basin.

3.5 Present status of Periyar-Muvattupuzha river system

The streamflow pattern in the river system depends on the downstream

releases from HEPs after power generation in addition to the respective catchment

yield. The Kerala State Electricity Board (KSEB) controls the operation of HEPs.

There is no integrated operation policy for HEPs in Kerala. The monthly power

generation from the Idukki HEP and the monthly total power generated from all

HEPs in the Periyar river basin was analyzed for a period of ten years (2000-09);

the monthly time series is given in Figure 3.3. The bar charts show a positive trend

31

Chapter 3. SYSTEM DESCRIPTION

in both the cases. The scatter plot of rainfall vs streamflow for the monsoon period

Figure 3.3: Power generation from HEPs in Periyar basin

show that the R2 value gradually comes down as the degrees of regulation increase

in the Periyar river (Figure 3.4).

Fifty six percent of the endemic fish of Kerala, classified under 32 species

is reported from the Periyar river, which makes the river basin a unique one in this

region (Arun 1998, Kurup et al. 2001). A fish survey in the Periyar and Muvat-

tupuzha rivers indicates that more than 50% of the ornamental/ food fish species

are critically endangered or endangered (Kurup et al. 2004). The construction of

15 dams has almost closed the river system to the movement of the biota through

the Periyar basin. Because of this fragmentation, many endemic and rare species of

fish occur as fragmented populations, isolated in headwater tributaries. Indiscrimi-

nate sand mining and pollution added negatively to such alterations (Sreebha et al.

2010).

Considerable degradation has occurred to the physical environment and

ecological conditions downstream of the Periyar river. The assessment on the health

status of this river stretch made using indices such as physical Habitat Quality (HQ),

water quality and index of biotic integrity (IBI) classifies the river health under the

poorest category (Kurup et al. 2001). The indicators for the Periyar river (Smakhtin

et al. 2007) gives a status summary for the river (Table 3.3).

32

Chapter 3. SYSTEM DESCRIPTION

Figure 3.4: Monsoon rainfall vs streamflow in the Periyar river basin

33

Chapter 3. SYSTEM DESCRIPTION

Table 3.3: Indicators for Periyar river basin*

Indicator Value Score Justification and comments

Rare and Very 5 Fishes critically endangered(5 nos),

aquatic biota high threatened (14 nos),extinct (14 Nos);

(Arun 1998; Kurup et al. 2001)

Unique Very 5 56% of endemic fishes of Kerala reported

aquatic biota high from Periyar (32 species);

(Arun 1998; Kurup et al. 2001)

Diversity of Very 5 Many threatened fish species inhibit in

aquatic habitats high pools, streams, runs and cascades;

(Arunachalam 2000)

Presence of Very 5 The river flows through Periyar wild life

protected and high sanctuary. 30% of basin area is covered with

pristine areas dense pristine forests)

Sensitivity of High 4 Multiple dams reduced flow leading to

aquatic ecosystem decline in fish diversity and algal bloom;

to flow reduction (Joseph 2004)

Percentage of 30-50% 3 30% of the watershed is covered with dense

watershed under natural forests; (Joseph 2004)

natural vegetation

Degree of 20-50% 3 Calculated as the ratio of the total

flow regulation storage capacity (3.27 BCM) to long-term

mean annual flow volume at outlet (12.3 BCM)

Percentage of basin 70-100% 1 Construction of 15 dams have almost closed

closed to movement the river system to movement of the biota

of aquatic biota

Fish Species Very 5 The basin is very rich in fish species

relative richness high (208 out of 287 species in the Western

ghats(70%); (Joseph et al. 2004)

Overall water Class B 5 Water quality in upstream and middle reaches-

quality Class B, Lower reaches Class C;

(Singh and Anandh (1996)

*Source: (Smakhtin et al. 2008)34