Based on monthly data from 55 meteorological stations from the North Pacific Watershed, seven annual rainfall trends were estimated and analyzed using non-parametric tests. The estimated slopes were analyzed in a geographic context to determine a potential spatial arrangement. Finally a brief analysis of the potential vegetation response from the different physiographic regions and the implications in the productive analysis is discussed. The findings indicated divergent trends in all the proposed variables, in general increasing and drier trends were found. Latitude was the most relevant factor regarding trend behavior in geographic terms. The lack of awareness and apathy from the authorities in the region were found, plus the regional vulnerability may originate notorious and serious consequences if the proper measures are not taken into account.
Within the context of climate change, it has been implied that one of the most evident consequences is the modi- fication of the water cycle [
Rainfall is of paramount importance for biological responses and distribution of almost all terrestrial living organisms. Vegetation is crucial in almost all ecosystems, since it is the first link of the trophic chain. Rainfall is a key element that determines relevant parameters of the vegetation such as its distribution [
The biological responses due to climate change have been widely documented [
For Sinaloa at this point, there is not a study that illustrates the behavior of rainfall variables within the frame of climate change. This analysis can place a basis not only for Sinaloa, but inside a regional context of northwest México, given that the main factors that drive the climate machinery of Sinaloa also affect a great portion of the cited region. The importance of this analysis not only relies on the ecosystem processes, but also on productive activities such as agriculture, fisheries and cattle production, which are the main economic activities of Sinaloa. The purpose of this work is to examine the rainfall trends and its associated variables, its relationship with their geographic location and to briefly explore the potential effects on its main vegetation types and agriculture ac- tivities consequences.
Sinaloa is a Mexican province located at the northwest Pacific coast of Mexico. Its long-narrow shape, that makes latitudinal change more prominent than longitudinal, is bounded in the west by the Sea of Cortés and by the Sierra Madre Occidental in the east (
Rainfall patterns in the Sea of Cortés eastern coasts, increase in seasonality as one moves to the north, this pattern is mainly determined by a monsoon regime [
In Sinaloa, three major physiographic regions can be clearly identified: the Coastal Plains, the Sierra Foothills and the Sierra Madre [
Desert [
A consideration must be taken regarding the position of some stations used for this analysis, the altitude of certain stations do not match the position within a particular physiographic region, this is due to its geographic location, as an example, Culiacán and Mocorito among others sites are placed within the SF region and their re- spective altitudes are below 100 masl, but these sites are spatially surrounded by hills and inside the cited re- gion.
Potential modification of the structure and composition of the vegetation and its association to climate change is discussed by [
In southern México, [
The monthly data of 55 weather stations was provided by the Comisión Nacional del Agua (CNA) (
To determine the existence of a trend of the rainfall variables proposed and to measure the magnitude of the change in each station, the Mann-Kendall test and Sen’s slope calculations were performed on each annual time series. The Mann-Kendall test is a non-parametric test that does not requires a normally distributed set of data. A thoroughly description of this method is detailed in [
To describe the behavior of the rainfall variables slopes in geographic terms, two analyses were performed: 1) a multiple linear regression analysis, using the slope values as dependent variables and latitude and altitude as independent variables, in order to estimate the β-standardized values; and 2) a spatial correlation analysis esti- mating the Moran’s I Index. Finally, a principal component analysis (PCA) is performed in order to elucidate the most relevant aspects regarding the variability of rainfall processes in this region.
Opposing trends were detected for all the rainfall analyzed variables. 37 stations displayed PP negative drying trends, eight were significant. Only three stations presented increasing significant rends (MZT, TPB and URQ). Divergent trends have been already characterized at a more extended spatial scale by [
Four potential scenarios can be drawn from the interaction between PP and PCI. A first situation with de- creasing PP and increasing PCI trends is the most frequent in this region, this combination hints a less amount of annual rainfall distributed in a more irregular fashion throughout the year, probably stretching the drought length. This situation is found in 28 stations, scattered mainly from the mid to southern and eastern regions of the ana- lyzed area. Eight stations were found with decreasing PP and decreasing PCI trends. This combination can sug- gest a drought-prone situation, due to a less amount of rainfall more evenly dispersed in temporal terms, wor- sening things in an already seasonally dry environment. Given the markedly seasonal nature of the rainfall in this region, an increasing PP and increasing PCI trend combination could pose an even more extreme situation with an equally or higher amount of rainfall in a less number of rainfall events, in some studies decreasing rain- fall trends have been associated with the increase in intensity of rainfall events [
Site | Abbreviation | Years of Data | Region | Latitude N | Longitude W | Altitude (m) |
---|---|---|---|---|---|---|
Acatitán | ACT | 1962-2012 | SF | 24˚05' | −106˚40' | 132 |
Ahome | AHM | 1962-2007 | CP | 25˚55' | −109˚10' | 10 |
Bacurato | BCT | 1980-2009 | SF | 25˚51' | −107˚52' | 234 |
Boca Toma | BCTM | 1962-2007 | CP | 26˚04' | −108˚46' | 36 |
Badiraguato | BDG | 1962-2012 | SF | 25˚20' | −107˚32' | 235 |
Cerocahui | CRCH | 1959-2006 | SM | 27˚18' | −108˚03' | 1500 |
Choix | CHX | 1962-2012 | SF | 26˚44' | −108˚20' | 234 |
Culiacán | CLN | 1956-2012 | CP | 24˚47' | −107˚25' | 60 |
Dimas | DMS | 1963-2012 | CP | 23˚43' | −106˚47' | 19 |
El Carrizo | ECRZ | 1966-2007 | CP | 26˚16' | −109˚03' | 20 |
El Cazanate | ECZT | 1967-2006 | SF | 25˚49' | −108˚01' | 930 |
El Comedero | CMD | 1981-2012 | SF | 24˚37' | −106˚49' | 238 |
El Dorado | EDRD | 1970-2010 | CP | 24˚19' | 107˚21' | 11 |
El Fuerte | EFRT | 1959-2010 | SF | 26˚25' | −108˚37' | 84 |
El Mahone | EMHN | 1962-2005 | SF | 26˚30' | −108˚35' | 135 |
El Playón | EPLY | 1962-2012 | CP | 25˚13' | −108˚12' | 5 |
El Quelite | EQLT | 1980-2012 | CP | 23˚33' | −106˚28' | 40 |
El Rosario | ERSR | 1964-2012 | CP | 22˚59' | −105˚51' | 32 |
El Sabino | ESBN | 1966-2005 | SF | 26˚29' | −108˚44' | 123 |
El Salto | ESLT | 1997-2012 | SF | 24˚07' | −106˚41' | 160 |
El Varejonal | EVRN | 1962-2012 | SF | 25˚06' | −107˚23' | 177 |
El Vergel | EVRG | 1975-2006 | SM | 26˚28' | −106˚23' | 2740 |
Guadalupe y Calvo | GCLV | 1959-2006 | SM | 26˚06' | −106˚58' | 2316 |
Guamúchil | GML | 1953-2012 | CP | 25˚28' | −108˚05' | 50 |
Guasave | GVE | 1974-2012 | CP | 25˚33' | −108˚28' | 36 |
Guaténipa | GTP | 1965-2012 | SF | 25˚20' | −107˚13' | 350 |
Higuera Zaragoza | HZGZ | 1962-2006 | CP | 25˚58' | −109˚18' | 9 |
Huites | HTS | 1962-2006 | SF | 26˚53' | −108˚21' | 214 |
Ixpalino | IXP | 1965-2012 | SF | 23˚58' | −106˚36' | 65 |
Jaina | JAN | 1962-2012 | SF | 25˚53' | −108˚01' | 194 |
La Concha | LCNC | 1961-2012 | CP | 22˚32' | −105˚27' | 21 |
La Cruz | LCRZ | 1993-2012 | CP | 23˚55' | −106˚53' | 30 |
La Huerta | LHRT | 1969-2012 | SM | 25˚21' | −106˚42' | 670 |
Las Tortugas | LTTG | 1974-2012 | SF | 23˚05' | −105˚50' | 131 |
Las Truchas | LTRC | 1962-2012 | SM | 24˚10' | −105˚58' | 1794 |
Los Mochis | LMCH | 1957-2010 | CP | 25˚48' | −109˚00' | 14 |
---|---|---|---|---|---|---|
Mazatlán | MZT | 1971-2012 | CP | 23˚12' | −106˚25' | 5 |
Mocorito | MCT | 1965-2012 | SF | 25˚29' | −107˚55' | 85 |
Navolato | NVT | 1968-2012 | CP | 24˚45' | −107˚43' | 14 |
Otatitán | OTN | 1982-2012 | SF | 23˚00' | −105˚40' | 148 |
Pericos | PRC | 1962-2009 | CP | 25˚05' | −107˚41' | 54 |
Potrerillos | POT | 1969-2012 | SF | 23˚27' | −105˚49' | 1470 |
Ruiz Cortines | RCTS | 1964-2006 | CP | 25˚42' | −108˚43' | 20 |
San Diego Tenzaens | SDTZ | 1973-2012 | SM | 24˚52' | −106˚07' | 1489 |
San Joaquín | SJQN | 1978-2012 | SF | 25˚40' | −108˚02' | 140 |
San Juan | SJN | 1990-2012 | SF | 25˚29' | −107˚50' | 112 |
Sanalona | SNL | 1962-2012 | SF | 24˚48' | −107˚09' | 137 |
Santa Cruz Alayá | SCA | 1962-2012 | SF | 24˚29' | −106˚57' | 120 |
Siqueros | SIQ | 1966-2012 | SF | 23˚25' | −106˚23' | 55 |
Surutato | SRT | 1961-2012 | SM | 25˚48' | 107˚34' | 1400 |
Tamazula | TMZ | 1959-2012 | SM | 24˚56' | −106˚58' | 254 |
Topolobampo | TPB | 1963-2008 | CP | 25˚36' | −109˚03' | 34 |
Tubares | TBR | 1974-2005 | SM | 26˚56' | −107˚58' | 321 |
Urique | URQ | 1968-2008 | SM | 27˚10' | −107˚55' | 599 |
Vasco Gil | VSGL | 1967-2012 | SM | 25˚08' | −106˚21' | 2417 |
flashfloods and severe erosive events, specially on sites with steep slopes. Finally, the mixture of increasing PP and decreasing PCI occurred only in stations above 25˚N in CHX, ECRZ, ECZT, EVRG, GCLV, GML, LCHM, TBR and URQ. This condition can suppose a less severe situation where a larger amount of annual rainfall is more evenly distributed along the year. The interaction of PP and PCI trends is shown in
The amount of PPS is the most important fraction of the year, not only in terms of quantity but also as the main driving element for ecosystem processes. 31 stations developed negative drying trends, but only EPLY, GVE and ESBN were significant. On the other hand, LTRC, NVT, TPB and URQ presented significant increas- ing trends (
Although in terms of quantity PPW is not strictly important, its amount can reflect the condition of ecosystem processes. If winter precipitation is considerable, it can diminish the effects of the drought length. Nevertheless, the winter rainfall regionally known as Equipatas are no longer as frequent as they used to be, mainly in the mid and southern areas within the analyzed watershed, only14 stations developed increasing trends, none of them was significant and all were located above 25˚N (
Given the importance of orography in rainfall [
graphic effects, with an increase in annual rainfall in elevated areas and an increase of drought length in lowland sites within a watershed, a similar result were found in this analysis, the increasing slope values of PP are largely associated to altitude. However, for the remaining variables estimated, latitude is a more conspicuous element in the geographic distribution of rainfall variables trends; longitude was the most relevant geographic element for PPS and DS slopes trends distribution. A potential explanation may be the larger magnitude of change in latitu- dinal way instead of altitudinal (
An analysis estimating I Moran’s index, shows that the trends of PCI, PPW, and %PPW developed significant clustered spatial distribution, the remaining variables trends tended to be dispersed (
This result requires further research at a more fine-grained level of measurement.
After rotating the data from a PCA analysis, three major components are retained. The matrix component loadings are shown in
Even when in Sinaloa and within this watershed the physiographic regions are plainly defined mainly based on altitude, and these conditions play a significant role on climate conditions [
Factor | PP | PCI | PPS | PPW | %PPW | PP < 15 | DS |
---|---|---|---|---|---|---|---|
r2 | 0.059 | 0.190 | 0.035 | 0.153 | 0.126 | 0.127 | 0.029 |
Latitude | 0.049 | −0.550 | 0.157 | 0.612 | 0.321 | −0.471 | −0.003 |
Longitude | −0.165 | −0.162 | 0.180 | 0.264 | −0.047 | −0.230 | 0.165 |
Altitude | 0.183 | 0.003 | 0.082 | −0.227 | −0.046 | −0.052 | −0.114 |
PP | PCI | PPS | PPW | %PPW | PP < 15 | DS |
---|---|---|---|---|---|---|
−0.0108 | 0.0321 | −0.0281 | 0.0357 | 0.0738 | −0.0012 | −0.0210 |
Component | PP | PCI | PPS | PPW | %PPW | PP < 15 | DS |
---|---|---|---|---|---|---|---|
1 | 0.863 | *** | 0.910 | 0.377 | *** | *** | −0.686 |
2 | 0.643 | −0.486 | 0.340 | 0.894 | 0.832 | *** | *** |
3 | *** | 0.750 | *** | *** | −0.364 | 0.867 | 0.362 |
opposite trends.
In Sinaloa, the largest economic activity is agriculture, which due to its geographic position and marked seaso- nality is highly dependent on water availability, temperature are strongly correlated with vegetation and soil. In order to increase the productivity, the first area to be broadly affected was the CP, where the thorn forest was cleared, in the late decade of the 50s and early 60s the rate of clearings increased with the construction of dams and irrigation channels mainly from mid to north Sinaloa. In the Sierra Foothills a more intense rate of vegeta- tion removal took place in the late decade of the 60s and early 70s, clearing the tropical dry forest for temporal agricultural purposes, and an artisanal but increasing and generalized production of charcoal has been occurring since the decade of the 80s to the present days. In the Sierra Madre region, the main problem is logging, either illegal or purposely legal but without any kind of control. The sum of these processes in Sinaloa is reflected by the elevated deforestation rate: 11000 ha∙y−1 which is one of the highest in México [
Regarding agriculture, [
The increasing irregularities and shrinking amounts of rainfall in a large portion of the analyzed area, may place the ecosystem functions and water availability in a situation of growing concern for the determination of natural resource management. According to a report developed by [
and consequently with social implications. Naturally, the ecosystems in northwest in Sinaloa and northwest México are seasonally productive, but in a fast-changing environment, subject to drying trends and global warm- ing, biological responses and productive activities are increasingly exposed to growing severe conditions, im- posing harder circumstances to achieve a minimum of regular responses and turning them almost impossible to reach. Given the high vulnerability of the ecosystems encompassing this region, besides a very poor water man- agement in a naturally drought-prone situation is urgent to evaluate at a more detailed level the mechanisms go- verning the entire regional process of change, to create a theoretical background to propose and execute mitiga- tion, conservation and restoration programs. Furthermore, by not recognizing or ignoring the mechanisms of this process and adding the poor natural resource management, the feedback created will only make things worse, creating a growing environmental problem with ultimately social unrest, since the most vulnerable people live in poverty and is the largest fraction of the population [
We want to thank Carlos Alberto Rendón and Artemisa García Garnica for his helpful assistance at the CNA.