Chapter 2 Physical and Socio-Economic Conditions 2.1 Physical Conditions
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Volume II; Part I Master Plan Chapter 2 Physical and Socioeconomic Conditions CHAPTER 2 PHYSICAL AND SOCIO-ECONOMIC CONDITIONS 2.1 PHYSICAL CONDITIONS 2.1.1 GEOLOGY AND TOPOGRAPHY The Cordillera Septentrional (Northern Range), sometimes called the Sierra de Monte Cristi, is a very long and narrow chain, lying closely to the northern coast. The highest peaks have eleva- tions between 1,000 and 1,200 meters above the mean seawater level (M.S.L.). The range rises abruptly from the inland plain, called Cibao Valley, which separates it from the Cordillera Cen- tral. This plain averages about 32km in width and stretches about 240 km across the country from the Bay of Manzanillo in the northwestern corner to the Bay of Samana in the northeast. The plain is drained to the northwest by the Rio Yaque del Norte and to the east by the Rio Yuna and its tributaries. The low divide between the two river systems, near Santiago de los Cabal- leros, has ground elevations about 180 to 200 meters above M.S.L. The eastern part of the plain is called La Vega Real, or Royal Plain, a fertile region that provides the nation’s main food sup- ply. South of the Cordillera Central is the Sierra de Neiba. This short range, about 100 km long with moderate elevations to about 2,300 meters, runs parallel to the Cordillera Central and is sepa- rated from it by the broad valley of San Juan. Santiago City area comprises hilly lands, small ravines and flat lands, with surface elevations ranging from 253 m above M.S.L. at hilly sides (Cerros de Gurabo) to as low as 160 m above M.S.L. at the areas along the Yaque del Norte River. Ground surface slopes are in general mod- erately sloped toward the River to flow surface stormwater runoffs by gravity either directly or through drains and streams. Dry clay strata cover most part of the Area, with gravel layers at many locations. The dense ground soil in Santiago is generally hard and has a high bearing capacity to support the struc- tures. However, the soil is liable to be eroded by water flows. This region has experienced no large-scale earthquakes in the past, and the buildings are designed for normal conditions but no particular precaution is taken against the seismic activities. Because of these unique topographic conditions prevailing in the Area, most of the sewers can flow the wastewaters by gravity toward the wastewater treatment plants (WWTPs) except those in small low-lying areas. Groundwater elevation is generally low particularly in hilly areas, but in the low-lying areas it is relatively high particularly during wet seasons when stormwater run- offs inflow to such areas. 2.1.2 METEOROLOGY (1) Climate and Weather The climate in the Dominican Republic is influenced by latitude, prevailing winds, altitude, and proximity to the sea. Because the country is part of an island, its temperatures are not so ex- tremely hot or cold as in continental countries, and provide relatively high average temperature in the year. Temperatures are constantly high near sea level, but cooler in elevated interior areas. The weather in the Study Area remains tropical throughout the year, with slight variations divid- ing into basically two seasons, summer and winter. The “hot season” starts in May lasting until October with temperatures rising to 31℃ or higher during day time and drop to about 22℃ at night. The so-called “cool season” is from November to April with relatively low precipitation and humidity. From June to November, tropical low pressures and Hurricanes occasionally M2-1 Volume II; Part I Master Plan Chapter 2 Physical and Socioeconomic Conditions cause serious damages to people and commodities. (2) Temperatures The yearly mean temperature in Santiago City is at around 25.7 ℃. The table below shows 10- year mean air temperatures in Santiago City recorded at an altitude of about 200 meters above the mean sea water level. The monthly temperatures vary between the minimum monthly mean of 24.5℃ in January and the maximum monthly mean of 28.5℃ in August. Temperatures are generally low during the cool months and higher during the summer months. Monthly Temperatures in Santiago City (1991-1998) (oC) Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Average 24.5 25.0 25.6 26.1 27.1 28.3 28.3 28.5 28.0 27.6 26.3 24.6 26.7 Maximum 29.3 30.1 30.8 31.3 32.0 33.3 33.3 33.8 33.4 33.0 30.9 29.7 31.7 Minimum 19.5 19.8 20.5 21.0 22.1 23.3 23.3 23.3 22.6 22.2 21.3 19.6 21.5 Source:Romon Isidro Rodrigues Taveras (2000); El Rio Yaque de Norte, Desde el Pice Doorte o o hasta Montecristi, at about 19.43 N, 69.70 W, altitude of 200m above mean sea level. (3) Humidity and Precipitations There are two seasons in the Region, wet season starting in May and extending into November and the dry season extending from December to April. High humidity is more common during the summer season; however, the difference between the two seasons is not always consistent. Sometimes there are weeks without any rain at all, except occasionally during night, while other times there are patches of rainy and overcast weather for a few days at a time. The average monthly precipitations, maximum daily precipitations, and frequency of rainfalls, which occurred over the past eight years (1991 to 1998) in Santiago City, are shown in the table below. The average annual rainfall during the period is 779.2 mm, whereas in February, the dri- est month in the year is with the average precipitation of 32.9 mm. The wettest month is May with the average precipitation of 118.8 mm. Precipitations in Santiago City (1991 – 1998) Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Average(mm/m) 71.4 32.9 81.8 81.2 118.8 36.9 45.0 42.1 54.9 103.2 59.4 51.6 779.2 Max. daily(mm) 73.6 22.8 88.3 81.9 78.6 50.3 45.6 62.3 58.0 72.4 92.01 61.1 Date occurred 1/1/98 20/2/94 15/3/93 14/4/92 20/5/95 2/6/93 24/7/93 16/8/95 10/9/96 6/10/95 10/11/98 30/12/97 Source: Romon Isidro Rodrigues Taveras (2000); El Rio Yaque de Norte, Desde el Pice Doorte o o hasta Montecristi, at about 19.43 N, 69.70 W, altitude of 200m above mean sea level. 2.1.3 HYDROLOGY (1) Yaqued del Norte River The Yaque del Norte River is the largest river in the country, which originates in the Cordillera Central, and flows down toward the northwesterly direction stretching about 290 km, finally in- flowing to the Atlantic Ocean at Bahla de Monte Cristi. The River covers a total tributary area of 7,053 km2 with flow rates ranging 25 ~ 40 m3/sec. The River tributary area includes Cibao plain, where agricultural productivity is the highest in the Dominican Republic. The farmland develops mainly from the City of Santiago to the down- stream of the River. In this downstream tributary area, irrigation systems have been developed M2-2 Volume II; Part I Master Plan Chapter 2 Physical and Socioeconomic Conditions since old times, and the farmlands with irrigation system reaches about 80,000 ha. The main agricultural products in this area are rice, sugar cane, coffee, cocoa, etc. In the down- stream river water is also used as the source for water supply in the City of Monte Cristi, hence, the River plays an important role not only as the irrigation water source but also as water supply source. The River is also an important ecosystem preservation zone. Most of the wastewater from the Santiago City is discharged to the river without receiving ap- propriate treatment. Recent information by CORAASAN indicates that the average water supply rate is 231,000 m3/day to the Santiago water service area, while the wastewater treatment capac- ity in the City is only 76,300 m3/day (30%). At present, most of the wastewater treatment plants have functional problems and remain either inoperable or abandoned. Under the circumstances, most of the wastewater is being discharged to the River without proper treatment. The monthly river flows released from the López Angostura Reservoir during 1997 and 1999 ranged from 17.3 m3/s to 120.11 m3/s, as shown in the table below: Water Flow Rate of the Yaque del Norte River (m3/s) Year Month At Lopez La Charcas Canal UFE Canal Ms Bo- Intake for Total Angostura 4km upstream (B1) gaert (B2) Irrigation Discharge (A) (B=B1+B2) (A-B) 1997 February - 27.23 - - - - March - 33.02 --- - April - 38.93 --- - June - 24.32 --- - July - 25.30 --- - August - 22.79 --- - September - 17.57 --- - October - 15.35 --- - 1998 Janaury 21.80 - 6.184 3.141 9.325 - February 17.32 18.395 7.540 4.286 11.826 6.569 March 19.99 17.747 4.770 2.326 7.096 10.651 April 20.38 - 4.795 2.034 9.829 - May 21.68 22.603 6.446 3.428 9.874 12.729 June 24.55 17.188 9.638 4.475 14.113 3.075 July 26.77 - 8.755 4.061 12.816 - August 19.10 - 11.089 3.800 14.889 - September 40.43 26.124 15.668 5.654 21.322 4.802 October 45.73 Flooding 6.226 3.739 9.965 - November 62.55 48.326 9.056 4.204 13.260 35.066 December 71.46 Flooding 8.440 4.279 12.719 - 1999 January 61.27 25.597 16.768 4.982 21.750 3.847 February 46.30 45.991 17.229 5.530 22.759 23.232 March 107.53 38.701 16.052 4.929 20.981 17.720 April 99.93 35.001 16.809 5.530 22.339 12.662 May 103.96 - 15.690 4.910 20.600 - June 116.48 - 13.499 4.347 17.846 - July 67.74 - 18.818 4.623 23.441 - August 61.55 - 21.448 5.480 26.928 - September 53.88 - 20.137 5.081 25.218 - October 61.00 48.625 16.131 5.049 21.180 27.445 November 27.23 27.753 11.474 5.061 16.535 11.218 December 120.11 51.830 - - - - Average 29.9 14.1 Maximum 51.8 35.1 Mimimum 15.4 3.1 Source: CORAASAN “Caudales Mensuales del Rio Yaque del Norte.” M2-3 Volume II; Part I Master Plan Chapter 2 Physical and Socioeconomic Conditions (2) Tributaries to the Yaque del Norte River The Yaque del Norte River has many branches across the Santiago City area.