effects of land use changes on reservoir sediment yields ... · effects of land use changes on...

Effects of land use changes on reservoir sediment yields: HPP Itumbiara,

Brazil

Marta Pereira da Luz, PhD.Lindsay Catherine Beevers, PhD.

Alan James Stewart Cuthbertson , PhD.Gabriela Maluf Medero, PhD.Viviane de Souza Dias, Eng.

Diego Tarley Ferreira Nascimento, M.Sc.

Beijing, 2016

Introduction• Soil erosion/land degradation: significant

environmental and economic impacts.• In fluvial systems with large anthropogenic

interventions sediment deposition can beexaxerbated by large impoundments.

• Consequences: reduced potential for hydropower production, less water for irrigationsupply, decreasing the efficiency of the reservoirsystem, etc.

Luz, M.P.; Bevers, L.C.; Cuthbertson, A.J.; Medero, G.M.; Dias, V.S.; Nascimento, D.T.F. 2

Introduction• In agricultural watersheds, inappropriate cultivation

practices often accelerate erosion rates and therebyincrease sediment movement.

• The occurence of large areas of exposed soils betweencultivation seasons influences ground infiltration rates and overland surface flows, thus potentially increasingsignificantly soil erosion rates (Lenhart et al., 2003; Lin et al., 2007).

• Implementation of best management practices isthefore required in these critical erosion prone areas tocontrol such losses and to protect receivingimpoundments from high sediments loads (Mishra et al., 2007, 2009; Mishra and Kar, 2012; Sardar et al., 2014).


Introduction• The Governament of Brazil is currently investing

heavely in large hydropower plants to meet theincreasing energy demands of the country;

• In an attempt to address this issue, engineers are involved in developing better management strategies to identify critical regions within thesurrounding watersheds and propose possible landuse changes to manage water and sedimentresources more effectively.


Objective• Identify specific erosion prone areas within a case

study watershed: HPP Itumbiara, Brazil, and toinvestigate the efficiency of the identified potentialbiostabilisation methods on sediment yield.


6

2082 MW – Installed Capacity778km² - Reservoir Area12,454 km³ - Useful Water Volume

Study Site: HPP Itumbiara Brazil

Luz, M.P.; Bevers, L.C.; Cuthbertson, A.J.; Medero, G.M.; Dias, V.S.; Nascimento, D.T.F.



Watershed5685km²

Sub-basins275


Figure 1 – Study area. Susceptibility for laminar erosion process – HPP Itumbiara Brazil



Figure 2 – (a) Land use; (b) topography; (c) soils and (d) digital elevation model.


Methods

Parameter Description Rank Sensitivity levelCn2 Initial SCS runoff curve number 1 ExcessiveUSLE_P USLE eqn support 2 HighSol_Z Soil Depth 3 HighEsco Soil evaporation compensation 4 HighSlope Average slope steepness 5 HighSol_Awc Available water capacity 6 HighCanmx Max canopy storage 7 High

Blai Max potential lead area index 8 High

Biomix Biological efficiency 9 WeakSurlag Surface runoff lag time 10 WeakSlsubbsn Average slope length 11 Weak

Variable Ranking Original CalibratedCn2 1 4.25 11.90USLE_P 2 2.90 3.97Sol_Z 3 1.31 0.66

Table 1. Result of sensitivity analyses

Table 2. Calibration parameters


Methods

0

2

4

6

8

10

12

14

0

5

10

15

20

25

30

35

40

45

5001

/04/

2013

06/0

4/20

13

11/0

4/20

13

16/0

4/20

13

21/0

4/20

13

26/0

4/20

13

Sedi

men

t (t

on) Observed Data (sediment)

Calibrated Data (Sediment)Calibrated Data (Flow)Observed Data (Flow)

Figure 3. Calibrated (simulated) and observed sediment delivery and flow from Subbasin 71.


MethodsFour different scenarios were devised to understand the potential benefits for erosion mitigation from implementing this grass biostabilisation as watershed-scale buffer strips at the HPP Itumbiarasite:• Baseline Scenario: Existing model with no additional vegetation• Scenario 1: incorporation of a 20 m wide buffer strip around the

sub-basin out fall into the reservoir (note: this buffer strip comprises Indian grass at the outfall of critical watersheds, avoiding existing forested areas);

• Scenario 2: incorporation of a 40 m wide buffer strip around the sub-basin out fall into the reservoir;

• Scenario 3: incorporation of a 100 m wide buffer strip around the sub-basin out fall into the reservoir;

• Scenario 4: incorporation of a 200 m wide buffer strip around the sub-basin out fall into the reservoir.

• The scenarios were modelled by changing the land use beside the reservoir to implement the buffer strip (Figure 4).


Methods

Figure 4. Baseline land use plus buffer with Indian grass.


Results

Indian grass buffer

Subbasin Area(ha)

BaselineSed.

(ton/year)

20m 40m 100m 200mSed.

(ton/year)Reduction

(%)Sed.

(ton/year)Reduction

(%)Sed.

(ton/year)Reduction

(%)Sed.

(ton/year)Reduction

(%)

23 1,766 3,693 3,683 0.27 3,679 0.38 3,663 0.81 3,643 1.3530 1,154 2,272 2,265 0.31 2,262 0.44 2,251 0.92 2,237 1.5446 1,719 3,619 3,593 0.72 3,589 0.83 3,541 2.16 3,489 3.5964 5,167 10,004 9,998 0.06 9,996 0.08 9,986 0.18 9,974 0.3067 3,318 2,386 2,382 0.17 2,381 0.21 2,374 0.50 2,366 0.8471 1,960 2,468 2,445 0.93 2,436 1.30 2,425 1.74 2,385 3.3682 1,628 3,682 3,669 0.35 3,663 0.52 3,643 1.06 3,605 2.09

Sum. 16,712

28,124 28,035 0.32 28,006 0.42 27,883 0.86 27,699 1.51

Table 3. Sediment yield results


Results

10,00 7,00

26,00

6,00 4,00

23,00

13,0014,00

10,00

30,00

8,00 5,00

32,00

19,00

30,0021,00

78,00

18,0012,00

43,00

39,00

50,00

35,00

130,00

30,00

20,00

83,0077,00

0,00

20,00

40,00

60,00

80,00

100,00

120,00

140,00

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

23 30 46 64 67 71 82

PAST FRSE FRST FRSD AGRL WPASWATR URML 20 m (ton/ano) 40 m (ton/ano) 100 m (ton/ano) 200 m (ton/ano)

Subbases

Figure 5. Decrease of sediment delivery per sub basin (and Land use designation breakdown), demonstrating the implementation of varying buffer strip widths.


Results

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

0 50 100 150 200

23 30 46 64 67 71 82Se

dim

ent D

eliv

ery

redu

ctio

n(%

)

Figure 6. Rate of reduction of sediment delivery with different buffer radius.


Discussion• Each sub-basin has particular characteristics which

influence its sediment transport capacity and subsequent delivery including; distribution of land use, slope, percentage of coastal area to the reservoir, and soil type.

• This makes the analysis complex. • However from the results it is clear that planting

Indian grass at the reservoir subbasin outfalls can contribute to a reduction of carried sediments and this is a non-linear relationship with each sub-basin showing a different reduction potential.


Discussion• It is clear that providing buffer strips of Indian grass

on the margins of the HPP Itumbiara reservoir results in a reduction in sediment transportation into the reservoir.

• This finding demonstrates the usefulness of buffer strip implementation for reservoir management in erosion susceptible areas.

• Studies, such as the one reported here, can provide a useful insight into the role of land use management practices on sediment yield.


Discussion• Relatively low percentage of sediment transport

reduction in the outfall of each subbasins was observed due to the introduction of the Indian grass.

• This shows some degree of contribution by the introduced methodology but also demonstrates the need for further investigation of potetial other alternatives of soil use and adoption of larger areas of permanent preservation.


Conclusions• To adequately and effectively target and implement erosion

control measures to reduce reservoir sedimentation, distributed erosion modelling can be used to support the decision making.

• However, the availability of sufficient data to calibrate and validate streamflow and sediment dynamics is crucial for successful application of such models.

• The presented methodology and results indicate that distributed erosion and sediment yield modelling with SWAT, supported by sufficient data on discharge and sediment yields of different points in time and space, can provide quantitative insight into scaling up the effectiveness of site-specific erosion control measures and the subsequent benefit to downstream reservoir sedimentation.

• Thus, this paper presents a first step towards evaluating the role of buffer strips on sediment yield, demonstrating the benefit of scaling up alternative techniques to treat erosion in reservoirs of hydroelectric plants.


Acknowledgements• The work was supported by National Council of

Scientific and Technological Development (CNPq) through the program Science without Borders.

• National Agency of Electric Power (ANEEL).• Eletrobras Furnas Company.


谢谢你Thank you!

[email protected]

Luz, M.P.; Bevers, L.C.; Cuthbertson, A.J.; Medero, G.M.; Dias, V.S.; Nascimento, D.T.F.

mailto:[email protected]

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