Table of Contents

Volume 2. Manggahan Sub-basin ...... 3 Geographic Location ...... 3 Political and Administrative Boundary ...... 4 Land Cover ...... 6 Sub-basin Characterization and Properties...... 8 Drainage Network ...... 8 Sub-sub basin Properties ...... 8 Water Quantity ...... 10 Stream flow ...... 10 Water Balance ...... 10

LIST OF FIGURES Figure 2-1 Geographical Map ...... 3 Figure 2-2 Political Map ...... 6 Figure 2-3 Land Cover Map ...... 7 Figure 2-5 Sub-sub basin Map ...... 9 Figure 2-6 Stream Flow, 1990-2004 ...... 10 Figure 2-7 Water Balance Percentage, 1990-2004 ...... 11

LIST OF TABLES Table 2-1 Geographic extent ...... 4 Table 2-2 Area Distribution of the Component Cities and Municipalities ...... 4 Table 2-3 Population Distribution by City/Municipality, 2000 ...... 4 Table 2-4 Sub-basin's Population Share to Total City/ Municipality, 2000 ...... 5 Table 2-5 Area Distribution of Land Cover ...... 6 Table 2-6 Some Relief Features and Other Geo-Morphological Parameters ...... 8 Table 2-7 Manggahan Sub-sub basin properties ...... 8 Table 2-8 Yearly Water Balances based on model simulation (mm)...... 11

Technical writer Engr. Cornelio O. Gamara, Jr., LLDA-PDMED

Technical editors Ms. Adelina C. Santos-Borja Engr. Emiterio C. Hernandez Officer-In-Charge Officer- In Charge Resource Management and Development Officer Project Development Management and Evaluation Division

Map production Mr. Neil V. Varcas, LLDA-PDMED

Volume 2. Manggahan Sub-basin

Geographic Location The Manggahan Sub-basin encompasses areas of the cities of , Marikina, and Pasig and the municipalities of and Taytay, province of . The total area of the Manggahan Sub-basin is about 8,760.904 hectares majority of which covers the municipality of Taytay followed by the City of Antipolo (Figure 2-1)

The sub-basin covers four of five barangays of Taytay and almost covers the entire municipality. The other cities and municipalities have the following coverage in terms of their land areas: Antipolo City =7%, Cainta = 35%, Marikina City = 61%, and Pasig City = 48%.

Source: LLDA GIS Figure 2-1 Geographical Map

Table 2-1 Geographic extent CORNERS NORTHING (UTM) EASTING (UTM) Upper Left 1607512.87500 305401.56250 Upper Right 1607512.87500 293934.87500 Lower Right 1622617.87500 293934.87500 Lower Left 1622617.87500 305401.56250 Source: LLDA GIS

Political and Administrative Boundary The Mangahan sub-basin falls within the political jurisdiction of eight local government units – three cities and five municipalities. It covers the southern part of Antipolo City, central portion of Marikina City, upper section of the municipalities of Taytay and Cainta (north of the Manggahan Floodway), and the western border of Pasig City. Antipolo City and the higher portions of Marikina City comprise the upper regions of the sub-basin. The downstream portions are mainly in Taytay, Cainta and, Pasig City. Two of the LGUs in the sub-basin are part of the National Capital Region (Marikina and Pasig City) while the rest are part of Rizal Province.

There are 48 barangays either wholly or partly covered by the sub-basin. It includes 13 of Antipolo City’s 16 barangays, nine of Marikina City’s 14, five of Taytay’, all of Cainta’s seven, four of Pasig City’s 31and one each for Teresa and San Mateo (Table 2-2).

Table 2-2 Area Distribution of the Component Cities and Municipalities Municipality/City Number of Barangays Area, ha Percent Antipolo City 13 2,706.01 31.67 Cainta 7 1,266.53 14.82 Marikina City 9 830.43 9.71 Pasig City 4 911.98 10.67 Taytay 5 2,329.94 27.26 5 376.76 4.40 Teresa 1 0.15 1.75 San Mateo 1 132.33 1.54 Total 48 8,544.13 100 Source: LLDA GIS

Table 2-3 Population Distribution by City/Municipality, 2000 Total Population in MW Household Number of Household Population Households in Size in MW Number % Share In MW MW Antipolo City 417,946 34.9 416,247 86,808 4.8 Marikina City 296,809 24.8 295,523 60,523 4.9 Taytay 128,000 10.7 127,139 27,546 4.6 Cainta 242,511 20.2 242,137 51,863 4.7 Pasig City 112,910 9.4 112,676 25,538 4.4 Total 1,198,176 100.00 1,193,722 252,278 4.9 Source: National Statistics Office

Majority of the populations of Antipolo City, Marikina City, Taytay and Cainta were within the Sub-basin. LGUs with the highest population shares were Cainta (100%) and Antipolo City (88.8%) (Table 2-3).

Table 2-4 Sub-basin's Population Share to Total City/ Municipality, 2000 City/Municipality Total Population Population in MW Number Share % Antipolo City 470,866 417,946 88.8 Marikina City 391,170 296,809 75.9 Taytay 198,183 128,000 64.6 Cainta 242,511 242,511 100.0 Pasig City 505,058 112,910 22.4 Total 1,807,788 1,198,176 66.3% Source: National Statistics Office

Barangays with the largest populations were Concepcion Uno (76,736) and Parang (66,469) in Marikina City which are at the headwater area as well as San Juan (91,196) and San Andres (61,708) in Cainta at the floodplain area. Nonetheless, Concepcion Uno’s population was still about half that of the most populated in the country, Barangay 176 (Bagong Silang) in Caloocan City. The distribution of population according to barangay per city/ municipality is shown in the following table:

Source: LLDA GIS Figure 2-2 Political Map

Land Cover There are six classes of land cover in the Mangahan Sub-basin: plantation, grass, built-up, arable, brush, marshy and water (Table 2-5). About (91.55%) of the watershed is classified as built-up, i.e., residential, commercial and industrial use. The second biggest land use in the sub-basin is grassy, i.e., suitable for agriculture or predominantly agriculture in usage Figure 2-3.

Table 2-5 Area Distribution of Land Cover Land Cover Area (Ha) (%) Built-up 9,687.04 91.55 Plantation 16.08 0.15 Grass 594.41 5.62 Arable 103.94 0.98 Brush 137.84 1.30 Water 41.57 0.39 Total 10,580.88 100 Source: LLDA GIS

Source: LLDA GIS Figure 2-3 Land Cover Map

Sub-basin Characterization and Properties

Drainage Network The drainage map of the Manggahan Sub-basin is shown in Figure 12-4 while the important watershed characteristics and geomorphological features are in Table 2-6.

Table 2-6 Some Relief Features and Other Geo-Morphological Parameters Parameters Values Area (ha) 8,760.904 Perimeter (m) 4,5093.134 Total number of streams 31 Total length of streams (m) 8,8397.797 Stream Density (stream/ha) 0.00354 Drainage Density (m/ha) 10.0900 Constance of Channel Maintenance (ha/m) 0.0991 Length of Overland Flow (m) 5.045015 Source: LLDA GIS

Sub-sub basin Properties

Table 2-7 Manggahan Sub-sub basin properties Sub-sub basin Name Area (Ha) Perimeter (m) SSB-2A 604.163 12817.998 SSB-2B 1387.743 22715.323 SSB-2C 156.565 5036.108 SSB-2D 1601.493 28601.504 SSB-2E 573.451 13272.709 SSB-2F 2206.026 41009.110 SSB-2G 186.674 5674.819 SSB-2H 666.971 13947.263 SSB-2I 623.093 12485.352 SSB-2J 754.726 11873.098 Source: LLDA GIS

Source: LLDA GIS Figure 2-4 Sub-sub basin Map

Water Quantity

Stream flow Stream flow refers to the discharge measurement at a given gauging station. It is simply computed as velocity multiplied by the cross-sectional area of a river or stream. Usually velocity is measured either by using a stream gauge, or using current or float methods. This is usually expressed in cubic meters per second (cu. m/sec). Highest recorded stream flow was in year 2003 with 6.7877 cu m/sec while lowest flow was observed in year 1997 of only about 0.9088 cu m/sec (Figure 2-6).

Source: LLDA PDMED` Figure 2-5 Stream Flow, 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 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 Manggahan 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 57.1% of the total rainfall becomes surface run-off, and about 34.5% of rainfall is lost as actual evapotranspiration. The base flow component of the total run-off is quite minimal, with only about 11.4% of rainfall, while the remaining 3.5% is stored as soil moisture and contributes to groundwater aquifer (Figure 2-7).

Table 2-8 Yearly Water Balances based on model simulation (mm). Actual Evapo- YEAR Rainfall Direct Runoff Baseflow Change in Storage transpiration 1990 2,278 703 1,308 394 (127) 1991 2,450 612 1,616 235 (12) 1992 2,401 610 1,467 245 79 1993 1,906 526 985 250 145 1994 2,241 691 1,356 285 (90) 1995 2,136 600 1,106 269 161 1996 1,449 672 644 204 (70) 1997 759 585 204 106 (137) 1998 975 441 334 51 149 1999 2,001 652 1,107 130 112 2000 2,985 761 1,902 318 5 2001 2,623 738 1,512 298 76 2002 2,768 756 1,668 302 42 2003 3,042 650 2,026 325 40 2004 2,085 681 1,093 271 40 Average 2,140 645 1,222 245 27

Source: LLDA PDMED Figure 2-6 Water Balance Percentage, 1990-2004