Table of Contents

Volume 11. Pangil Sub-basin .................................................................................................. 3

Geographic location ................................................................................................................ 3

Political and Administrative Boundary ..................................................................................... 4

Land Cover ............................................................................................................................. 5

Sub-basin Characterization and Properties............................................................................. 7

Drainage Network ............................................................................................................... 7

Sub-sub basin Properties .................................................................................................... 9

Water Quantity ......................................................................................................................10

Streamflow .........................................................................................................................10

Water Balance ...................................................................................................................11

LIST OF FIGURES Figure 11-1 Geographical Map ..................................................................................................................... 3 Figure 11-2 Political Map .............................................................................................................................. 5 Figure 11-3 Land Cover Map ........................................................................................................................ 6 Figure 11-4 Drainage Map ............................................................................................................................ 8 Figure 11-5 Sub-sub basin Map of Pangil Sub-basin ................................................................................... 9 Figure 11-6 Streamflow, 1990-2004 ........................................................................................................... 11 Figure 11-7 Water Balances based on model simulation, 1990-2004 ........................................................ 12

LIST OF TABLES Table 11-1 Geographic Extent ...................................................................................................................... 4 Table 11-2 Municipalities and Barangays Covered ...................................................................................... 4 Table 11-3 Population Distribution by Municipality, 2007 ............................................................................. 4 Table 11-4 Area Distribution of Land Cover .................................................................................................. 6 Table 11-5 Some Relief Features and Other Geo-Morphological Parameters ............................................. 7 Table 11-6 Pangil Sub-sub basin properties ............................................................................................... 10 Table 11-7 Streamflow Data, 1990-2004 .................................................................................................... 10 Table 11-8 Yearly Water Balances based on model simulation (mm) ........................................................ 11

Technical writer

For. Azyleah C. Abino, LLDA-PDMED

Technical editors Ms. Adelina C. Santos-Borja Officer-In-Charge Resource Management and Development Officer

Engr. Emiterio C. Hernandez Officer- In Charge Project Development Management and Evaluation Division

Map production

Mr. Neil V. Varcas, LLDA-PDMED

Volume 11. Pangil Sub-basin

Geographic location The Pangil sub-basin is located at the eastern part of the Laguna de Bay basin. It is bounded by the Siniloan sub-basin on the north, east bay of the Laguna Lake in the west and to the southeast is the Caliraya sub-basin. Seven municipalities coming from two provinces are located within the sub-basin, namely Kalayaan, Lumban, Paete, Pakil, Pangil and Siniloan in the Province of Laguna and Real in Quezon Province. Figure 11-1 illustrates the geographic location and boundary of the Pangil sub-basin in the Laguna de Bay.

Source: LLDA GIS

Figure 11-1 Geographical Map

The whole sub-basin has a total area of 5,585.63 hectares, with a basin length of 14.73 kilometers (km) bounded with 52.98 km perimeter length having an average width of 5.71 km. The geographic extent of the sub-basin is presented in Table 11-1.

Table 11-1 Geographic Extent

CORNERS NORTHING (UTM) EASTING (UTM)

Upper Left 1582649.75000 344442.56250

Upper Right 1582649.75000 332602.43750

Lower Right 1596894.85196 332602.43750

Lower Left 1596894.85196 344442.56250 Source: LLDA GIS

Political and Administrative Boundary

The Pangil sub-basin covers 27 barangays located in seven (7) municipalities, six of which are situated in Laguna and one in Quezon Province (Figure 11-2). Pangil is the largest municipality accounting for almost 50% (2,674.62 hectares) of the total area of the sub-basin (Table 11-2). In view of barangays covered, Pakil has the most with seven (7) with an area of 816.41 hectares or 15.09% of the sub-basin, followed by Pangil with six (6).

Table 11-2 Municipalities and Barangays Covered

MUNICIPALITY NO. OF BARANGAYS AREA (ha) PERCENTAGE (%)

Kalayaan, Laguna 3 815.46 15.07

Lumban, Laguna 4 59.48 1.10

Paete, Laguna 2 782.13 14.45

Pakil, Laguna 7 816.41 15.09

Pangil, Laguna 6 2,674.62 49.42

Siniloan, Laguna 4 170.17 3.14

Real, Quezon 1 93.40 1.73

TOTAL 27 5,411.67 100.00 Source: LLDA GIS Based on the 2007 Census of Population by the National Statistics Office, the total population within the Pangil sub-basin is estimated at 63,563. Pangil, having the largest area percentage making up the sub-basin, also shared the highest number of inhabitants with 36% or 23,187. It is followed by Pakil with 32% or 20,040 residents. Pakil has the most number of barangays (7) within the sub-basin. On the other hand, Lumban is the least populated at 341 (1%) though there are the four (4) of its barangays located within the jurisdiction of the sub-basin. Table 11-3 shows the detailed population data of each municipalities as well as the annual growth rate.

Table 11-3 Population Distribution by Municipality, 2007

MUNICIPALITY POPULATION ANNUAL GROWTH RATE (%)

Kalayaan, Laguna 3,795 1.10

Lumban, Laguna 341 1.28

Paete, Laguna 13,583 0.98

Pakil, Laguna 20,040 1.62

Pangil, Laguna 23,187 1.72

Siniloan, Laguna 2,616 2.14

TOTAL 63,562 National Statistics Office, 2007 Census of Population

Source: LLDA GIS

Figure 11-2 Political Map

Land Cover Approximately 1,420.18 hectares or 25% of the Pangil sub-basin are covered with forests. However, the land validation activities as well as the analysis of the satellite image revealed that there are no more pristine or virgin forests in the sub-basin, only open forests exist. Other dominant land covers are brushland and plantations either by coconut or other agroforestry species. Brushland covers about 23% or 1,279.35 hectares while coconut/agroforestry plantation is estimated at 22% or 1,221.58 hectares. The built-up area composed of almost 15% or 831.66 hectares. Table 11-4 shows the land cover distribution in the sub-basin of Pangil while Figure 11-3 shows the land cover map.

Table 11-4 Area Distribution of Land Cover

LAND COVER AREA (ha) PERCENTAGE (%)

Urban 831.66 15%

Forest 1,420.18 25%

Arable 462.55 8%

Plantation 1,221.58 22%

Grassland 80.97 2%

Brushland 1,279.35 23%

Marsh 290.19 5%

TOTAL 5,586.48 100% Source: LLDA GIS

Source: LLDA GIS

Figure 11-3 Land Cover Map

Sub-basin Characterization and Properties Drainage Network The drainage map of the Pangil Sub-basin is shown in Figure 11-4 while the important watershed characteristics and geomorphological features are in Table 11-5.

Table 11-5 Some Relief Features and Other Geo-Morphological Parameters

Source: LLDA GIS

PARAMETERS VALUES

1. Area (ha) 5585.663

2. Perimeter (m) 52982.151

3. Total number of streams 29

4. Total length of streams (m) 50854.329

5. Stream Density (stream/ha) 0.00519

6. Drainage Density (m/ha) 9.1044

7. Constance of Channel Maintenance (ha/m) 0.1098

8. Length of Overland Flow (m) 4.5522

Source: LLDA GIS

Figure 11-4 Drainage Map

Sub-sub basin Properties

Source: LLDA GIS

Figure 11-5 Sub-sub basin Map of Pangil Sub-basin

Table 11-6 Pangil Sub-sub basin properties

SUB-SUB BASIN NAME AREA (Ha) PERIMETER (m)

SSB-11A 321.303 8164.845

SSB-11B 339.808 9429.827

SSB-11C 247.975 9555.525

SSB-11D 496.276 10072.559

SSB-11E 523.415 11588.588

SSB-11F 309.317 8435.548

SSB-11G 157.462 5973.008

SSB-11H 146.616 5581.476

SSB-11I 301.607 7765.399

SSB-11J 427.146 8719.570

SSB-11K 149.832 5460.211

SSB-11L 186.614 6953.386

SSB-11M 1978.602 34367.859 Source: LLDA GIS

Water Quantity

Streamflow The yearly average streamflow of the Pangil sub-basin from Year 1990 to Year 2004 is illustrated in Table 11-7 and Figure 11-6 wherein the highest peak flow can be observed in Years 1998 and 1999 with almost 10.61 m3/sec and 10.07 m3/sec, respectively. On the other hand, the lowest was recorded in Years 2001 (1.90 m3/sec) and 2003 (1.73 m3/sec). From 1991, the trend is increasing up to Year 1996; however declined on Year 1997 but peaks on the following year until Year 1999 and set the highest recorded data for the 15 year period. The Figures show, on the other hand, that the average streamflow again significantly decreased on the succeeding years.

Table 11-7 Streamflow Data, 1990-2004

YEAR STREAMFLOW

1990 5.831371

1991 4.484427

1992 5.162482

1993 6.574756

1994 5.718763

1995 8.595945

1996 7.345572

1997 4.13708

1998 10.61002

1999 10.07319

2000 2.857765

2001 1.904581

2002 2.178424

2003 1.731301

2004 4.735935 Source: LLDA PDMED

Source: LLDA PDMED

Figure 11-6 Streamflow, 1990-2004

Water Balance The Sacramento Soil Moisture Accounting (SAC SMA) Hydrologic Model is used to simulate watershed rainfall-runoff relationship and to generate the long-term water balance of the 24 sub-basins of Laguna de Bay. The SAC SMA accounts for all water entering, stored in, and leaving a drainage basin. Though many parameters are used in this water balance accounting process, precipitation has the main impact on runoff.

For Pangil River Basin, the long term water balances of the basin based on the hydrologic simulation is shown in the table below

. The 15-year average would show that 64.85% of the total rainfall becomes surface run-off, and about 20.98% of rainfall is lost as actual evapotranspiration. The base flow component of the total run-off is quite minimal, with only about 11.76% of rainfall, while the remaining 2.41% is stored as soil moisture and contributes to groundwater aquifer (Figure 11-7).

Table 11-8 Yearly Water Balances based on model simulation (mm)

YEAR RAINFALL ACTUAL EVAPO-TRANSPIRATION

DIRECT RUNOFF

BASEFLOW CHANGE IN STORAGE

1990 4,093 804 2,770 473 46

1991 3,445 858 2,065 409 113

1992 3,837 872 2,396 480 89

1993 4,703 858 3,202 474 170

1994 4,131 902 2,607 563 59

1995 5,878 835 4,297 537 209

1996 5,154 897 3,489 620 147

1997 3,270 944 1,733 530 62

1998 7,054 954 5,251 628 220

YEAR RAINFALL ACTUAL EVAPO-TRANSPIRATION

DIRECT RUNOFF

BASEFLOW CHANGE IN STORAGE

1999 6,574 807 4,883 714 169

2000 2,415 801 1,218 378 19

2001 1,877 804 782 299 (8)

2002 2,009 728 952 284 44

2003 1,713 739 709 274 (9)

2004 3,514 712 2,338 357 107

AVE RAGE 3,978 835 2,580 468 96

Source: LLDA PDMED

Source: LLDA PDMED

Figure 11-7 Water Balances based on model simulation, 1990-2004